Everything can be used for bad. Does someone who makes a knife feel bad about if it is used for murder or torture? Probably yes, I know I would, but do I feel guilty? Hell no. I cannot control what a bad person will do with my good thing. Encryption is no different, it can be (and is) used for good. Keeping people safe with secure communication is just one of those things. Yes that also means bad people can use it to plot an attack. It is unfortunate but there is no stopping its use. Terrorists have used encryption for as long as the "good guys" have.