This is one of the situations that would be better answered by experiment. I wouldn't mind being proven wrong, but I would like to know how exactly I am wrong. How exactly would a new violent baboon not disrupt the peace in the group?

Would he be like: "see, there is enough food, and no one is preventing me from eating as much as I want, so why don't I just relax and enjoy this piece of paradise"?

Or would he attack the other males, but when no one fights back, he would be like: "oh, this is so boring, and by the way there is enough food, so what don't I just relax..."?

Or would the other males fight him back, but despite their new first-hand experience with violence, they would keep the libertarian ethics that it is wrong to initiate violence, and it is only ok to defend oneself?

Or perhaps would the males in the group instinctively attack any other new male (even without him attacking first), but would maintain the peace among themselves?

There are many alternatives to return to global violence, but I would like to know which one of them will happen. Though, at this moment, the return to global violence seems the most probable option to me.