Please suggest good colleges for robust political debate

Yep, that is pretty much what happens when society moves from an honor or dignity based culture to one based on victim-hood. This trends was discussed in the following Atlantic piece.

http://www.theatlantic.com/politics/archive/2015/09/the-rise-of-victimhood-culture/404794/

Our current campus based victimhood culture has lead to Oppression Olympics in which various compete to see which is the most aggrieved as illustrated at a “Students of Color” conference at UC Irvine.

http://www.thecollegefix.com/post/30436/

In any case, if the OP wants a robust diversity political debate, one must look for a large institution that attracts a variety of students. Schools like Amherst or other northeastern LAC’s don’t offer that as they are effectively mono-cultures despite their claims to be diverse.