Been noticing that for quite a while now, each platform has their own cultures, even when there can be exchange between two or more. If an instance blocks another, I'd imagine it's due to differences in such cultures.

As an user for some 2 years now, I get an idea of the communities I'd rather avoid, but other than the most extreme examples, haven't seen much openly discussed about specific instances.

Now, I wouldn't worry about what people from instances x, y or z think if I were you. If you like how your chosen instance is, and people from other instances organize to hunt you down, seek your instance's support if needed, or simply block each and every one pestering you.