Some people just have aversion to Pink. I speak from personal experience.
Why do People Block?
I have blocked players, but not just for a friend request. Only if they are obnoxious and send insults. If I know you in real life and we trash talk in good fun it is one thing. But a nasty comment from someone I don't know in an online venue ... life is too short to tolerate those ______ (you fill in the blank)
Maybe sometimes the opponents style is just aggressive and bizarre mixed with some amateur failure behavior. This way it's really hard to learn chess so it can be better to block such opponent than getting in the position to play them again. Imho its thousand times better to lose against a double brained opponent than an unskilled player making stupid and strange moves
What would the MF mean? Mother Father? Anyways, I can't. I already changed my username. If you see my blog, then you'll know what I mean.