"Thanks for listening" strikes me as about right: they're taking an effort to seriously consider what you have to say, which is worth thanking regardless of whether they eventually agree with you. Thanking them for coming to a particular conclusion seems like it could disincentivize honest truth-seeking.

(Do make a point of thanking people if they listen to you, consider your ideas seriously, and eventually decide that they still disagree.)

This only works in the case where Alice went to considerable effort to provide a well-organized argument, as in your example. I'm not sure what to do in casual conversation.