There are a number of words I don't use in the standard way. For example, I use 'theory' very broadly. In general, I hope my meaning will become clear from my writing in general. But I use a very precise definition for 'coerce', so I'll give that now. It's from the TCS Glossary. The entry gives:
The psychological state of enacting one idea or impulse while a conflicting impulse is still active in one's mind.
In general, when one has conflicting theories, one adopts some temporary theory to avoid coercion. For example, one might stop and think about it. Or do one thing, while keeping the ability to switch choices open. However, people have limited creativity and this sometimes fails. Also, certain external circumstances can facilitate failure. Like being shot. (Conflicting theories along the lines of "I don't want to die" and "I haven't got a choice, so the other theory is wrong".)
Oh, and if you get robbed, you'll probably be coerced because you'll want to not be robbed, and also know that's pointless of you. However, if you get taxed, you probably won't be coerced, because it's easier to see taxes have some purpose and/or aren't worth the effort to fight, and thus reject the "I don't want to be taxed" theory causing the coercion.