I'm not open to that argument at all, I'm afraid. It places the power to make a wholly subjective judgement of what is or isn't 'offensive' and thus requiring of police intervention with individual coppers. That judgement is inevitably determined by factors such the political atmosphere and leanings of that policeman's superiors rather than by legal principle and thus becomes a means of stifling legitimate political expression from the side you arbitrarily decide are 'the bad guys'.