@lynne
My experience is a that a lot of people seek out those who don't explicitly declare their sarcasm and then proceed to verbally assault their character for notions the speaker didn't even align with from the beginning.

Declaring your sarcasm has become a literary self-defense mechanism against... Annoying people. I don't know how to even better-describe them at the moment. Calling them trolls would imply effort on their part- but that's being to generous.