The hardest thing for me is not when someone is complaining frequently about others telling them that they suck. There, you can find out sides of a story, resolve a problem, give constructive, creative feedback on why there is a lack of sucking and ways to make the self more flameproof...
But when someone goes off on the "I totally suck and I am a worthless piece of shit" tangent, I get all flamy and fumy to myself, because on the one hand I think they don't, on the other hand I think they should get over their inferiority complex and finally admit to themselves that they don't suck and face up to that, on the third hand I want them to admit that they don't suck so that they won't start sucking, and on the fourth hand I know that I hate it so much because I feel the same way sometimes and just have the decency to not show it in public.
Which sucks.