There are many words that can be introduced into a hate filled racist rant. Irrelevant.But what if you really disliked white people who got a suntan and became "lobsters". And you ended up using it as an insult. Would it then be racist to call them lobsters. This might be the crux of @motorbiking's argument.
Gammon is derogatory word. It is not racist. MBK specifically said it is racist - wrong.

