"How should we police the use of the word Hinayana?" If you like to follow a way of thoughts SOAsian people often thinks if confronted with wrong deeds, just use the thought: "If he/she/they would know, they would not do it." and you can practice a lot of metta in this case, for just the actor will receive the fruits, and its not a matter of doing knowingly or unknowingly. The second is even more hurtful.
As for the matter correcting wrongs, its more relevant to think about the precept of taking what is not given, which is actually a very blatant matter in the case of going into ones quote or text. And no, no TOS's are able to make this fact ineffectable and invalid.
There is nothing wrong in rebuking and criticizing wrong deeds, such as "apuñña", thinking on the less practiced way of merit Apacāyana.
But, and that is the "jumping point", such has no beneficial place, if it is not simply out of compassion for the doer, so that he could abstain in future or even take up the change to confess his transgression.
One needs to be aware, that people who use such, may it be knowingly or unknowingly, actually cut them off in a good manner, from having the possibility to get the good teachings ever known.
If you search for a discrimination between that what is used common under Dhamma and Adhamma, it's not worong to use the label Dhamma-Vinaya (Buddhas name of his "religion") and Buddhism. And there, under this label Buddhism, there is no way to find a beneficial classification of certain views, since this label is so broadly used. The most "neutral" way is for sure "northern" and "southern" Tradition or Buddhism, is one likes to classify in a way of certain opinions. But don't forget, like the Buddha told: "The most insecure measure of judgement is the own opinion."
And don't forget, you have no, really now task to police, or course there is a certain duty to help, entertaining/maintaining one self inside of a certain community. So as you might see, most faults are made of those "good intentions" (based on assessments, one can prevent others from the "bad guys" or their ripping fruits).
When ever you are able to be most mindful and able to keep it alive, do never police but try to help in ways which are not causing mostly much heavier misdeeds.
Don't forget! At least such a usage is for others a good hint, that the use is not informed about the Buddhas teachings, which is one information you would cut of, even for the support of the user him self.