It's certainly not immature to not like the idea of spending time around people with different politics.
UoY is significantly more right-wing than many universities in the country. It is largely distant from the NUS and I would describe it as completely isolationist and uninterested in the national conversation at this point. Being involved in the NUS myself has given me a lot of insight into the stark difference between this university and many others, not only in the political views of the student body but also in the general sense of apathy that I have not noticed anywhere near as strongly in the majority of other universities I've encountered.
Labour may be the biggest political society on campus (marginally larger than York Tories as of this year), but it's only centre-left and most of the members are not the biggest fans of Corbyn. I would say that York is, generally, very much grounded in the political centre.
It's not just 'politics', though. I and my friends have received a massive amount of harassment at York - including death threats, campus press publishing information from our facebook pages and innumerable misogynistic and transphobic personal attacks. I am also aware of racism on campus, though as a white person I have obviously never personally experienced it, so cannot comment on it. I would speak more about the situation, but I'm tired and find the entire topic distressing.
The only reason I am able to continue studying at this university is because I have a large support network, and there are a lot of people very engaged with liberation issues in the Women's, LGBTQ, Disabled Students' and BME Networks. Shout-outs to Palestinian Solidarity Society, Socialist Society and Feminist Society, too.