I guess I understand fans being upset, but all he’s really done here is say the quiet part out loud. Every person in the world probably has a similar attitude towards someone they have to deal with at their job. Anyone who actually thought referees were some sort of robots that were somehow above professional disagreements and resentments towards certain managers had their head buried a mile deep in sand. They’re required to disclose any club allegiances they have and don’t referee certain matches accordingly, but sentiments like this are just going to happen. They are human beings after all.
That said, he probably deserves the suspension simply for being dumb enough to allow this to get out to the public. That’s the biggest lapse in judgment in all this.