Personally I wouldn't want to work for a company actually detaining people, but call me terrible but I'm not sure I'd feel the same about letting them pay to host some code...
1. You provide tools to a group. 2. You believe (in a informed way) that the group intends to act immorally. 3. Your tools will make the group more effective at acting immorally.
Do you have any responsibility for what happens?
A) Have a means of identifying which of their users are pedophiles, rapists, and terrorists? B) Have a means of selectively denying people access to the tools? C) Have a means of determining which of these users would using their tools to rape, produce child porn, and enact terrorism?
If so, then yes, I would say they're guilty.
So everyone who chooses to license their software as open source is making a choice that intentionally limits their own ability to prevent others from using the licensed software legally. So no, open source software developers don't have the choice to restrict certain groups from using it - but that is because it was a choice they themselves made on how to license the software. Isn't that the ultimate hand washing?