Yeah Oda made them cartoonisly evil. And Garp be aware of this cartoonish evil doesnt help at all. Then again, Garp couldn't choose between duty and family in MF. He vehemently tried to make Luffy and Ace join the marines, got mad and then happy when Luffy and Ace became a pirates, did nothing about it, and then asked Ace why didnt he just become a Marine. Garp seems to have always been indecisive.