It is all very strange, as he started it with a ‘dig’ and doesn’t like the responses and the coverage he gets from it. If you have a genuine bullying complaint ( and there doesn’t appear to be one) then surely you do it directly via the appropriate channels and not publicly on twitter. If you don’t want to work with someone because of your views towards them then great. Just don’t spend the rest of your career complaining you haven’t got work or a ‘falling through the cracks’ for government handouts.
I suppose the bullying in the instance is not actually what Piers said , but the fact Piers quoted the tweet (when originally the tweet did not tag Piers and indeed his name was censored, so Piers would have had to go looking for it) which would then mean that some of Piers twitter followers would attack the guy in the hope of impressing him.
Morgan is a public figure with a big following, so it's arguable that he should know that even if he mildly insults or ridicules someone, people will take that as a invitation to do the same thing.