You're not substantially reinforcing their beliefs.

Well, yes, if we're talking about a single conversation, especially over the 'net, you are not going to affect much anything. Still, even if you do not reinforce then you confirm. And there are different ways to get mindkilled, entangling your identity with beliefs is only one of them...

On the other hand, sneaking new ideas into someone's internal memetic ecosystem tends to put stress on any totalizing identities they've adopted.

True, but the same caveat applies -- if we're talking about one or two conversations you're not going to produce much if any effect.

In any case, my line of thinking in this subthread wasn't concerned so much with the effectiveness of deconversion, but rather was more about the willingness to employ arguments that you don't believe but your discussion opponent might. I understand the need to talk to people in the language they understand, but there is a fine line to walk here.