This is my first time hearing about that. Many people are extremely stupid, so it makes sense some notion like that would be idiotic racist bullshit that various losers would believe.
Not really. I don't know what effect you thought posting the stereotype online in public was going to have other than to spread it. This is exactly and precisely what spreading it looks like, surely?
Why shouldn't racist (or sexist, etc) comments be called out? Just because you needed to fight with someone online today to make yourself feel better? Take it somewhere else pal I'm not buying.