I think felons should be allowed to vote. Yes, even terrorists who hate America like that 'Boston Bomber' Tsarnaev kid.
It's a slippery slope if we let law abiding decent people say "no no, you hate us, you want to kill us, so we don't want your input on how to run society."
I also think it's a slippery slope if we let hot young women say "no no, I won't have sex with you because you're a gross disgusting old man.