I really don't think the twins actually feel the Beekmans are "evil." I think they were throwing the word "evil" around humorously. When one of the Beekmans (can't remember which) called them "the evil twins," they were like, "Of course we're evil! We never claimed we weren't!" I really didn't get a sense of malice from them about it.
Neither did I. In fact, during the dog chow task, the twins pointed out that the Beekmans had always been 'nice' and were only now finding their inner 'evil gay' when they needed it most, while they (the twins) had always been 'evil'.
I never completely got over their walking off with the Rockers' money - though that turned out to be the least of James and Abba's problems in the end - but overall they were funny, energetic, pretty good racers (I suspect Killer Fatigue played a role in their defeat), and very honest about their own mistakes and shortcomings.