The emphasis to my eye was on the word "really". tptacek is suggesting that author of the previous post should consider whether they really mean that or if he they have merely taken a stance without thinking it through clearly.

Very different both in tone and implication from "You're an asshole for saying that".

Saying "If you honestly mean that then you're an asshole" is just a round-about way of calling somebody an asshole while providing them with an out; it's a method of insulting people to get them to change their stance. Where I come from, it's considered rude.

In fact, I wrote it the other way first, and but when I read it on the screen, it looked a lot like I was saying they were an asshole, and so ratcheted it back, since that wasn't what I was trying to say.

You were saying they were an asshole, in both versions. Trying to be coy about it doesn't change it. I'm not sure why you bothered to be coy about it since you regularly get away with incivility on this site.