PC before serving.

So I'm sorry if this has been asked before, but I wanted to know if it's really true that if you've served in the Peace Corp they will not let you serve in the armed forces afterwards. I'm about to be a senior in college and I want to serve. I'm split between the Peace Corp and the Navy (yes I know they are very different) and I have thought about doing the Peace Corp after college and then the Navy, however I was very surprised to hear someone say if you've been in the PC they won't let you into the Navy. Just wondering if there was any validity behind this, or some idiot running his mouth.