Unless it's morally against my ideals, like violating privacy, stealing money from kids with phones, etc., I don't see that many problems with features I don't agree with. They want it, they pay, why not? Surely, if it was my own company or a team I'd value, then I'd hesitate to implement that feature and argue with everybody about it. But at some point, I leave the project and once I don't I own it anymore, I don't have problems with features I don't like. That is, unless they tell me /how/ to solve the task.

What helps me most is finding a technical challenge that makes the feature interesting and fun to implement. This shouldn't be too hard, if you are free to design the feature technically. Hope that little hack helps you getting things done.