This was a concern we had when we were discussing how to handle pronouns, and it's the reason that we decided not to have a custom field option. Instead, our policy is that we'll add pronouns if someone requests them and they seem to be acting in good faith. We have a couple strange ones like doe/deer, but that's because a longtime user used them and requested them, and doe never showed any signs that doe was a troll.
What the other user said was part of our reasoning for adopting them. On the cases where we've had trolls come in and use them, they tend to go mask off pretty quickly and get banned, and we don't really care if they think their owning us somehow.
If you mean people use neopronouns to make people who hate neopronouns mad, I mean I don't know how to distinguish unless you're a mind reader but honestly who cares. You can use whatever neopronouns you want for whatever reason you want, unless it's mocking trans people.