Harsh;
Custom maps and custom settings, you a completely missing the point. Your assumption of a "stranger" joining your team and playing that way is true, I'll give you that. This is where the word "team" comes into play, open your mic up and talk to your team mates. If you find someone who can't plat as a team member then choose better players, the reality is it is an unrealistic feature of the game to curb just what your talking about, however it still doesn't change those type of players.
Sure, keep the flashlight on your head for the children, custom game servers, not so, and face it, that's just reality but you do have legitimate points, right on..