Personally, as a GM, I don't see it as my right to forbid anything. The only thing I can do is saying, that I will not gm for a particular player as long as the player plays that character. Not a very big difference, agreed, but imho there is a difference. As a GM, I think of myself as "only another player". I take the role of a gm, but that doesn't give me any right to decide about other people's characters. The only right I have, is to refuse to play/gm.
Uncouth + Charisma 1, for example, is imho one of the worse ideas you can have, as social interaction is a key ability for every shadowrunner. Adding cyberpsychosis is simply nonsense. With Charisma 1 + Uncouth alone, keeping your own connections from killing you will be one of the everyday adventures such a character will have...
In this case, it would depend on the question "Why"? I see 3 possible reasons:
a) Point Min-Maxing. I don't gm for people like that. Simple.
b) The player doesn't have enough experience to see that such a character would be a bad idea. I would talk to the player.
c) The player thinks, it's a good idea, has a good background for the character and knows how to roleplay something like that ("not talking, just shooting" is not the same thing as "roleplaying uncouth"). In this case, I would perhaps agree to gm with that character, but I would not want to promise that he'll survive long. Not that I would try to kill him actively, but let's be honest, such a character could survive in the real jungle very well, but probably not in the urban one for long.