With regards to the mocking of Sheldon by his friends, this was sadly a result of the post-Cheers comedy spectrum where, inspired by the sitcom ‘Friends’, sarcasm became the dominant form of humour.

In my experience friends might rib each other with in-jokes and such but they won’t actively be cruel to each other just to raise a laugh. If my friends were like this in real life I wouldn’t socialise with them at all.