And then responding to everyone by saying "but I want to talk about C1 and you're not talking about C1" gave it the appearance of downright trolling. If I didn't have previous familiarity with you, that's what I'd have assumed, actually.

You might say, "But they didn't directly address C1!"

But no one cared, at that point, what you wanted them to address. You didn't have enough credit built up with them to steer the conversation - and objecting that it wasn't going where you wanted it to go just pissed them off further. If you'd engaged with them on their points, you could have built up credibility. As it is, the post was just dropped into the void.