It means it would often lead to a barrier for children. I was a child who grew up with Tremulous so I wouldn't want to have that opportunity taken away from me, as quality servers taught me a lot. Toxic community (children including), if concentrated in one or several servers, will 'intoxicate' others.
It's a good feature of course, I am for it, but the problem is like I said - lack of quality servers for children, a place where they can learn new stuff, meet decent people, learn how to play with better players and eventually learn how to behave on the internet.