From what I understand, most people hate Daedra because of their actions or those of their followers. Dagon's followers destroy places; Molag Bal's spreads strife and disorder; Boethiah's followers commit murder, treason, rebellion; Clavicus twists your words and often makes each deal painful; Hircine only appreciates the strong and crafty; Namira's spheres are revolting; and Vaernima creates nightmares. The other Princes are less "evil" about their actions. Course they can still be quite painful to deal with at times. Azura for instance seems like a nice god to worship, but she doesn't really care all that much about her followers, only that they accomplish her plans. Sheogorath is well, insane. and Sanguine is indulgence incarnate. Mora is also somewhat "evil", not really caring about mortal lives.
Of course, I'll reiterate what the others have said in that the Daedric Princes aren't really good or evil. They're like people. When Molag Bal enslaves a soul, he doesn't know (or at least feels) that it's evil, just that it benefits him. Same even for Meridia, she doesn't care why you practice necromancy, she'll kill you anyway. Remember that she didn't start "life" as a Daedra, she was cast away from her "family".
EDIT: Oh and by "most" I mean the Empire at large; Khajiit and Dunmer revere certain Daedra.
I'm a lore noob, so I'm not sure if I'm completely correct.