Genuine answer: annoying people who inject themselves into social circles in which they’re unwelcome. And, no, I’m not defending bullying. I’m just explaining how it happens.
Yeah… This maybe isn’t the nicest way to phrase it, but I’ve seen similar situations. Usually people are just kind of talking behind people’s backs, but sometimes it gets nasty :(. Frankly people kind of get bullied all the time everywhere. It’s maybe not as violent as playground bullying but people will be shitty to people at work, school, whatever. Do your best not to be a part of it, try to be self aware if you might hurt somebody else’s feelings, and try to stand up for people.
Also the idiot with samurai swords on the wall and a lack of good hygiene skills.
Humorously enough, it wasn’t comp-sci for me. They were generally the cool tech bros, with some nerdy exceptions. The true neck-beards were a certain subset of physics students. They literally left keyboards greasy when they used the community computers. A friend who was in the higher classes told me classes usually had a couple feet section left blank around them because of the smell.