I disagree but I'm not sure that I can do that tactfully (nor briefly); so, my apologies in advance.
Exaggeration
I think the example is a bit extreme: it goes from zero to Godwin in a single post.
I read the implied/emotive premise as being that, if I don't "call out as (objectively) wrong" the statement that "Feminists are offended by Buddhism", then,
- I am complicit in (and perhaps approving of) the Shoah.
- One or little girls may choose a non-Buddhist life path (and so end up in hell)
- The situation is somehow analogous to when Thích Quảng Đức self-immolated
If that is your premise, if it's how you feel, then I guess that helps to explain why you feel compelled; and I'm sorry that you feel so distressed about it.
But I think it is an exaggeration of the situation. If you don't see the situation clearly, if you don't communicate the situation clearly, then I expect you'll be unable to resolve the problem with the other person.
Strawman
The statement in question i.e. "Feminists are offended by Buddhism" is, I guess, a misquote of the following statement:
I have not noticed anything you have posted that could be offensive.
While as a dhamma practitioner i never get offended, thank you for thinking of everyone here.
Getting offended what feminists claim happens to them.
As I read it, the statement isn't saying that "feminists are offended by Buddhism" ... it's saying that feminists claim they get offended, e.g. that "feminists" are inclined to say something like, "I am offended by X", or "X is offensive" (where 'X' isn't necessarily Buddhism), and in particular perhaps, "you are offensive" or "your statements are offensive, offend me."
If you won't read the statement in question then, if you oppose it, it's likely to be a typical straw man argument -- which I consider worthless and counterproductive behaviour.
Big picture
It's good to keep in mind the larger picture, the context of a statement. I read the quoted answer above as saying:
- I don't think you did post anything offensive (but if you did, you're excused ... I'm overlooking it, too slight to notice)
- As a Buddhist I tend not to take offense, but thank you for being considerate of everyone here
- When I think of "people getting offended" I tend to think of "feminists"
If you consider yourself feminist and want to disagree with the last statement, the best way to disagree might be by not claiming you got offended by the statement (otherwise you're just proving the point).
Straw man -- I'm worried about (I doubt) your ability to see the big picture. When you objected to the answer discussed in this meta-topic I got the impression that you focused on "no metta" rather than on "primarily equanimity".
Arguing -- Part of the "Big picture" on this site is that I don't want people arguing. I met a pacifist once when I was young, who said, "I'll discuss anything with anyone. But as soon as it turns into an argument, I walk away." I think that arguing is worse than not arguing. At the risk of posting a ridiculous/extreme (straw man) example of my own, imagine I posted some stupid answer, like, "Men are goats." If that were posted as an answer, I'd rather that readers of the site would see that answer with a simple "minus 1" vote next to it and no comments underneath -- I'd prefer that to a ton of comments arguing about whether men really are goats!
Always an excuse -- People always seem to find some excuse to go to war: "it's his fault, I'm in the right, we have to protect someone else, it's a moral obligation, think of the women and children, etc." All the reasons you give for arguing (e.g. "to prevent other people being misled") could also be given for any sectarian or religious argument (e.g. for arguing against Theravada doctrine, or against Mahayana, or etc.). But I just finished saying that I don't want sectarian arguments ... that I expect you to more-or-less, and at least, tolerate other people's views.
Ineffective
Assuming that this is the answer that you're talking about, there are 10 comments by 6 people under that answer ... the answer hasn't changed.
IOW people did try to object to the answer, and their objection was ineffective. People hardly even bothered to downvote the answer.
You might want to argue that the comments are worthwhile for posterity: someone who reads the answer can read the comments and see there were dissenting opinions ... that's not ideal from SE's point of view, where the useful information is meant to be in the answer and not buried in a ton of comments under the answer.
Equanimity
Let's get back to your alleged reason for arguing, i.e.:
When declared as a blanket statement, it can actually harm others. A young girl maybe chooses a different life path. A person on edge is nudged toward bad behavior.
Isn't that the old "Think of the children" argument (which some people associate with moral panic)?
Anyway, people are supposed to be adult (aged 13+) when they read this site. They ought to be able to make up their own mind about things they read.
Part of "equanimity" is the thought that each person is heir to their own actions. If someone does go to hell, it's not because you failed to "call out" some statement on the internet.
Feminism
I'm not sure it's on-topic but FYI you can see here to read some of Dhammadattu's statements about feminism and how that might relate to Buddhism.
Though there are some statements that I wasn't predisposed to agree with, they mostly make sense. They may not be my personal opinion, not the answer I would have given, but I think it doesn't make sense to expect everyone to have identical opinions.
There was one answer which I did disagree with -- see the comments which I moved to chat at the end of this answer. In that case it was because he was linking to a site which I thought was so non-Buddhist as to be objectionable. In that case I eventually persuaded him to remove the link; I don't know whether that was because of how I said it, or whether it's because I'm a moderator.
My guess is that part of the reason for my "success" there is that I was very specific/narrow about what I wanted changed, i.e. I wanted the link to that web site removed. I think I did it by persuading him that the link didn't support his argument, didn't say what he thought it did -- I wasn't trying to persuade him that his whole answer was wrong or that he should write something else.
Politics is off-topic
One of the things I learned during that chat is that I'm willing to quote splcenter.org whereas he is willing to quote conservapedia.com -- I take it, therefore, that there are some political or cultural differences in our backgrounds. That makes me disinclined to argue further, because political arguments are off-topic on this site: I couldn't go around claiming that this site is inclusive if I tried to forbid "conservative" views.
I could wish that he didn't seem to have thing about feminism (by "having a thing" I mean that the latest comment seemed to me gratuitous, unnecessary), but I suppose he knows that and it isn't my job (or yours) to criticize or censor every statement.
Summary
I don't think you should call out people's statements.
As you wrote earlier, "I'm new here, and hoping to better understand the cultural and participation norms".
I think the norm is that questioning a statement, asking for clarification, is OK, e.g., "I didn't understand X" or "I didn't understand Y".
It's also OK to suggest a specific improvement (i.e. "constructive criticism"), either as a comment ("This answer would be clearer if you mentioned X" or "I don't see why you mentioned Y, it doesn't seem relevant and detracts from the rest of the answer); or possibly be editing the answer yourself (but only if you're sure that such an edit would be welcome by the author ... I tend to only edit for grammar).
If you disagree with something then downvote it or post a better answer (but your answer should address the question, without directly referencing the answer you disagree with).
You can also post on Meta (to get input from other users), and/or flag it for moderator attention; I suppose the moderators aren't so new and do have some experience with the "norms".
Please note incidentally that the norms of this site are unlike those of many other SE sites -- see the FAQ index (summary of site policies). Note too that the goal of many of those policies is to "minimize controversy" -- you can help with that by "taking exception" to as little as possible.