Of course, when you "date up", those people will "look down" on you :-)

Why? Because you're chasing someone who's - somehow - better than you ("dating up" means exactly that), you know it (that's why you're chasing them) and they know it. So, even when they're nice people, they will acknowledge you're "lesser" than them.

E.g., on dating sites I sometimes see women who says "I'm looking for a cultured man", while their writing is far from articulate or fluent. So she's looking for a man who's more cultured that her, and he obviously will find her less cultured than him.

Why is that so surprising?!?

It's a bit like an average man chasing only very gorgeous girls, and then complaining they are not interested in him, or they look down on him... Dude, of course they do! They're better than you (and that's why you're chasing them).

Basically, if you want a relationship based on equality, you have to look for a partner that's your equal (isn't it logical?) - not someone who's obviously better than you.