Can 13 year olds play mature rated games

Can they yes but should they that's the question personally I think yes if they are mature enough to know what's real and what's fake also the blood in most games the kids are going to have to deal with it in life and I believe it shows them that you can't just hide your kids from life especially games life Call of duty Not letting play GTA or Fear where it scares the crap out of my 23 year old son I understand but come on let them live life without there friends giving them a hard time