Southgate said: "When all players go on the field they know they will be goaded at some point but there's a line and I think it was crossed. It's very hard to control when people do it in that vast number. I thought Mido did everything he could for our team.
"He reacted a little bit but he's a human being, that's understandable. He got back in control of his emotions very quickly. His conduct since has been exemplary, I'm very much in his corner, he's gone about things the right way.
"It stepped over the line of banter. I don't think it's necessary for Newcastle to apologise. I don't think a club can always take responsibility for the actions of their supporters."