How should a Buddhist approach honoring parents who abused them?
My father was a selfish alcoholic who physically abused me on several occasions, my mother was loving but would often be off putting because of anxieties. I see the error in their ways and have better insight to why they are who they are by practicing mindfulness and right view. I see them both as victims, my father trapped by drugs and selfishness, my mother by worry and fear. 

This helps me have strong love and compassion for both, because I can see their suffering and know its part of the human condition. I don't take it personal, remember attributes are not permanent, there are roots to why people act like they do and it can change. 

Recognizing someone suffers, is human, can be a great honor.