Briefly note the inappropriateness of the comment, point to the class ground rules (if it is appropriate) and move on with the lesson. If these comments persist, you might try making up a lesson on stereotypes and addressing the issue as a learning objective without targeting any individual. The goal is not to put a student on the spot publicly, but sometimes the comments need to be addressed somehow.
A way to do this is to create some lessons around them. More.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.