graycel hate is for a few reasons
1. as many have said, hierarchy. human nature to establish them and socially enforce them.
2. gate keeping. without gate keeping a community is nothing. you are being forced to conform to the community so you learn to fit in rather than try to impose your own stuff (this is important to prevent the slow push of LGBT shit)
3. grays are known to make the worst post. from obvious glowposting, to IT rage bait, to ascension threads after 50 posts, to humble bragging about their looks or female attention
4. jokes. it has become a running community joke to shit on graycels for everything even if it's not their fault
personally i can't be bothered to hate on grays and just judge people here based on what they say rather than post count or join date