I have to say it most certainly is bullying.
I work for a large company and just went through the same thing.
I put up for it for some time for my own reasons but decided recently enough was enough.
As it is a large company I put in a grievance.
Recently had the result of the investigation not entirely to my liking but they did agree with me somewhat and he is now going to be dealt with. Now I know that this most likely means that I could be seen as a trouble causer - but so what - we have laws for a reason so I figure if a person treats you like S&%t use them laws and dont let them get away with it.