Oh, you primates! Group aggression led by a high-status member against a perceived weaker member is really common among primates and some other mammals, particularly rhesus macaques and humans, as well as wolves.
In general, the high-status member initially is probing a newcomer for any signs of weakness. The newcomer may counter at a similar level, demonstrate submission and surrender, or even flee. The signs of weakness such as fleeing invite pursuit, and the dominant primate and their supporting band will tend to escalate their abuse.
https://www.psychologytoday.com/blog/beyond-bullying/201309/animal-rites-what-animal-behavior-teaches-us-about-bullyingThe behavior tends to be self-propagating as well. Recipients of abuse often become abusers themselves. This has been demonstrated with physical abuse across generations, and within group dynamics. Persons who have been marginalized by the larger social body often congregate and in turn marginalize others who they themselves see as weak or 'inappropriate' in some way.
In a recent example of this, I witnessed a large social support group for transgender folks go through this process. (Not a group I normally associate with, but one that has hosted large benefits in the recent past.) The majority of the group members consider themselves to be cross-dressers. A handful of members went beyond this, seeking medical intervention and surgery. They were marginalized, and recently forced out of the group as being unacceptable to the rest.
Humans tend to be slightly better at longer term planning than other primates, and their abusive behaviors may be more subtle. This is pretty ugly stuff to have to face, but it is real, and definitely out there.
As rational beings we all need to recognize this behavior in ourselves and others, and rise above the for the long term benefit of all. Just because someone lives their life differently than you do, or has different experiences and background, does not invalidate their existence, their need for support, their basic need for social contact. They are still people.
Welcome to the human race. It's not a competition.