Honestly, if I was in that situation, I would have punched that fucker in the jaw. This is unacceptable workplace bullying and harassment. Same sort of thing happened to me at work once, all be it just a 1 on 1 thing, what you went through sounds terrible. but I asked a work friend if he could get something for me and stuttered for maybe 3 seconds on the "get". So he lets rip with an imitation and it took all of my conscious efforts not to knuckle his jaw right there in front of 50 customers and staff members. I guess I'm lucky in that my 99% of my friends, both at work and socially, accept my stutter and don't really notice it, or if they do then they don't say anything. But seriously, fuck this guys. This needs to be reported to someone.