But money is just a tool, it doesn't have any morals. It can't be "good" or "evil".
Would I take money that was some time ago involved in something terrible. Yes.
Would I do so if by doing so I help someone doing this. No.
But with Bitcoin you can choose to "not ask" and thus never know that something is going to be used for evil. Is turning a blind eye the correct solution (ignorance is bliss)?
You are not asking with every deal you make with conventional money where it comes from, or what you a financing with this.
Imagine the cashier in the Supermarket would ask every customer where his money comes from.
Only when you get sketchy deals there is a point where you can tell there must be something wrong.
One reason I never "invested" one BTC into pirate was, that the only way I could explain his high rates was that he is either a scam, or gets his money from a source were I don't want to have any involvement. And it was the latter that restrained me (I'm greedy and stupid).