Well that is quite an amusing barometer when it comes to plenty of feminist slogans, statements, tweets etc... replace "men" with say "blacks" and they can come across as horribly racist. But men are fair game.
I guess if an advert were made teaching black people that it isn't OK to sell drugs, that gangs aren't cool - perhaps quoting some rap lyrics glorifying gang violence etc.. plenty of black people wouldn't be too happy about it given that those are things that are done by a small minority and aren't exclusive to black people either.
Of course you might also get a few black people who might otherwise be referred to as "uncle toms" saying - "well gang violence is bad and I identify with the good black people, I know this advert featuring black people doing loads of bad things isn't about all black people", "well the message is a good one still, don't be a drug selling gangbanger" etc...