Like if you hear them, you just don't care anymore and start going "a-huh" every few seconds to not be rude.
For me, it's usually politics. I just don't care about politics, and even if I did, I still wouldn't want to talk about it because you'll either be reiterating the same old talking points I agree with already, or the same old talking points I don't agree with at all. Either way, I'm not listening anymore until the subject changes.
Heavy cynicism of almost anything also shuts down my care-center. If I start hearing the phrase "lost my faith in humanity" or something like it, I can't help but think of you as a sad-sack who blames his/her entire species for his/her own misfortunes. Grow up, chump, and get over it. When you do, we can have a meaningful conversation again.