If someone screamed go back to my own country at me I'd have a really hard time not punching them. And yes, I live in a country that I wasn't born in so I can totally see this happening. Luckily my second home country is full of kind people and not assholes so in the 7 years I've lived here I've never experienced something like that. The worst I ever dealt with was someone laughing when my pronunciation sucked. I just asked him in his native language how many languages he could speak. Shut him up right quick.