I think to randomly block someone for no apparent reason is a generational thing for some people to do. People from older generations tend to be more tolerant of everyone around them, meaning they wouldn't typically block someone because they only associate with people who look like them.
Anyone born in the last 20 years however, are cut from a different cloth than the rest of us insofar as their social tolerances go. I have found that people who were born with a silver cellphone in their mouth who would always have their face planted in a cellphone screen during all waking hours, tend to be exceptionally socially inept in their real world outside the internet. This is because they don't know how to interact with human life in the real world because their real world only exists on the internet, not outside in real society.
Blocking people for no apparent reason on a site like SW becomes a way of coping with people when placed in unfamiliar territory of group socialization.