I really don't care how old you are. Your behavior in the team is what matters. It just so happens that younger players tend to be loud, obnoxious, and disrespectful. That's where the prejudice towards "squeakers"(such an ignorant term) comes from. One of the players I've spent most time with in destiny just happens to be 13 or so. He's very mature and respectful and that's why I prefer to have him on my team whenever we're both online.