Or maybe they think that words matter and if you care enough about something to be calling people to action maybe you should care enough to phrase your words so they're less ambiguous.

Not everyone reads things the same way, even if you think it's the obvious and only way to interpret something. If they did, there would be a lot less misunderstandings online.

Someone pointing out ambiguity is possibly helping you refine your point and message, so if you encounter it maybe try to read it less as someone being a pedantic asshole and instead someone helping you express your message more successfully. At a minimum it will likely help you keep a good attitude or emotional state, which is nothing to sneeze at.

It was rhetorical and snide. We all know there is no exclusivity. OP is just asking for action for the amount of already acquired information. He isn't saying we shouldn't acquire more evidence.

There is no ambiguity, just verbal gymnastics played by those who want to comment in bad conscience as if they have somehow furthered the conversation.