can anyone tell me why Dobey hates the family(Malfoys) that he serves?

Dobby was treated badly by the Malfoys so he was more likely to disagree with their values and be against them and their beliefs. On the other hand, Kreacher was treated well by the Blacks, especially by Regulus.

Well Dobby is always getting hit by Lucius and his cane. They always mistreated Dobby.
While Kreacher loved his family and Sirius's mother a whole lot he looked up to her. But the weird thing about him is that he wants his head up in a row with his mother or something but he liked his life.