If he was told not to play because some of Kemptown would be offended by the lyrics surely they could just turn the P.A. down a bit (assuming that those who would potentially be offended wouldn't actually be at the gig).
Although how loud would the P.A. have to be for those with the potential to be offended (assuming they are not actually at the gig)to hear him and make out what he is saying whilst in another building (assuming thy are not standing around in the street outside a gig where someone is filling the audience with hate towards gays) I have always found him very hard to understand at the best of times.