To add to that: Lots of people that would like to commit the crimes don't have the skills and they're more than happy to recruit those who do, either directly or through all kinds of obfuscation. The fact that 'someone else would otherwise do it' is absolutely no defense.

If you don't want to come out and point blank refuse you can always say that you can't do it because you're not that good. That's a perfectly valid excuse and one that I've used on occasion. (Long story, maybe one day.)