You can get plenty of information out of someone without laying a finger on them.
In my opinion the question is the extent to which it's OK to play with people's psychology through isolation and misinformation, while still giving them 3 hots and a cot. The important thing to note here is that you can still damage people this way if you take it too far; solitary makes people go crazy especially when they're being fed false info about what's going on outside the walls.
Then again, these guys did not get rolled up for signing too loud in church. They have valuable intel in their heads. We're not going to beat it out of them, but how far are we willing to go? Should they get the same rights and protections as suspects in the US judicial system? This is the conversation we should be having in my opinion.