Why I lose my temper with those who trivialise racism

This evening we had a fantastic evening walk about with Boris in Sloane Square. It was great to see the big man engaging with so many members of the public.
I must admit that I did lose my temper completely with a young man who started baiting me when I stayed on afterwards at the tube station to hand out leaflets. He was sitting on the fence, waiting for someone and started calling out "He's a racist" everytime I was handing out a leaflet. He kept on saying this. Now I think had he done this once or twice I would have just asked him if he had read the article and told his to stop trivialising racism. He was of course a white middle class, presumably lefty, who in absence of any decent political points to make just decided to call Boris a racist. After a few more provocations I walked up to him and started shouting at him, "how dare he trivialise racism. Did he understand what a terribe thing racism was and not something to be thrown about lightly by some idiot. Had he read the article, did he understand the context, did he understand what satire was? Racism is a horrible thing and Boris is no racist". It caused quite a gathering for a moment or two. Then of course he ran away, I believe he called me Mr Hitler as his parting gesture. He was probably not worth the energy. But it just infuriates me, as someone who is brown, who has experienced racism growing up in Liverpool during the 80s. Let's defeat racism, let's go after those people who preach hate and want to stir up racist sentiment, but never seek to trivialise it to make a cheap political point.