Seeing as he's saying banned over a game I'm assuming he means the master server, and the reason they're banned is because they don't follow the rules of the master server, and the rules aren't there for the sake of rules, they are there for a good reason.
For example, cheating normally as in giving yourself more rings is noobish but allowed, however doing things like modifieying your score so you'd always win race or match no matter what the outcome is not allowed, which is completely understandable.
But what you're probably refering to and propably is true are the hangouts and roleplaying servers that are banned. Well this game is not meant for just 5 year olds, or 10 year olds who act like 5 year olds, and is meant for everyone, but people who are teenagers and over can not enjoy hangouts and roleplaying since we're too mature for that, so its not allowed, especially now that most servers these days seem to be hangout or roleplaying, people who are mature and want to play, in a way can't, which is another reason why its not allowed.
Also its just commencence, you don't sit in, for example, a race map that has blatent checkered flags around and things like that telling you its race, yet you're sitting there thinking you can pretend to be in shadow's house making some tea, its just naturally retarded, and its common sense to know that it is, which is why we ban people for it. Its not doing the mode that's been put there for you and other people that want to do race can't.
If you're like five playing srb2 I can understand why you enjoy talking like you do when you roleplay, but there are some people aged like 10 and over who should definatly be more mature than that by now who still talk like they're five or little girls playing with a dolls house, you shouldn't be that age and still think its fun to talk like this.
"mummy chao prepares milk for tails hao" "YAY YAY milk, yum yum" "come and get it, its on the table" "tails chao drinks milk from bottle" "yay my belly welly is full" "mummy takes tails chao to bed" "goodnight mummy" "goodnight son". Its just like, aargh, its dumb, its not allowed, people older and mature than that want to actually play the game, and noobs who act like that can enjoy the proper modes of the game just as much, so there's no point in allowing roleplaying whatsoever.
And you should just naturally be playing the correct gametypes, there is no map that is designed for hangout, I can't remember if SA City was, but if so that was wrong, basically, every map created is for match, ctf, race or coop, so you should just naturally use those maps for what they're created for.
Sorry for that long rant, I bet someone else is going to come along and sum it up in only like two sentances and then lock.