I don't have all the details of the situations you mentioned, but I'll try and form an opinion anyway. Let me know where I'm wrong/missing facts and I'll re-evaluate.

I think there is a key difference in the situations you mentioned. In TyZi's situation, it sounds like multiple people came at him over the same problem that they had with him, that was (probably?) unique to TyZi. This is harassment. In the case of a staff member telling a community member "fuck you", it sounds like the insult thrown was not very personal at all. I doubt that the staff member in question had a history of throwing insults at the insultee, or continued to do so afterwards.

I think staff looks at the personalness of an insult to decide whether or not to punish the insulter. I also think that this is pretty reasonable.