Well, This is way off topic, but like Ramsay, I too am aggravated by the notion that commemorating certain parts of history somehow makes one a racist. So before it gets shut down I'll say this;

That fellow is wearing a tartan based on Royal Stewart, which is an emblem of Britain, being the personal tartan of Queen Elizabeth II. if I remember my history, the British Empire had the institution of slavery until 1833. So he can pick and choose where, and when, and by who, he should get offended.

It would be like anyone who's ancesters or kin were shot at by the 42nd Regiment of Foot or the Black Watch getting all bent every time somebody wore a goverment sett kilt. And don't say that was ancient history, The Black Watch were involved "the Troubles" in the 1970s.