Today’s cartoon in the Daily Mail, drawn by Mac, has caused a lot of hand-wringing on social media for apparently comparing refugees to rats. I can’t agree. As a cartoonist, I would argue that he doesn’t appear to be saying that all migrants are rats, simply that some rats are slipping through among the migrants – and I certainly don’t have a problem with him characterising Isis fighters as rats.

Personally, I rather doubt that many well organised terrorists would submit to the lottery of being trafficked into Europe on unseaworthy boats followed by a long march across the Balkans. But while I disagree with his opinion - and don't think it a particularly good cartoon either - I certainly don't find it disgusting. I'm also rather worried that sections of the supposedly left or liberal PC brigade seem to be as keen to censor cartoonists as some of the more brutal right wing dictatorships.

Recently I was fortunate enough to meet the Malaysian cartoonist Zunar in London. The following day this incredibly brave man was flying back to Malaysia to face trial and possibly a lengthy jail term for daring to criticise the government through his cartoons. He was voluntarily submitting himself to that trial - even though many countries had offered him asylum - in order to make a stand against censorship; as he is fond of saying, “how can I be neutral, even my pen has a stand?"

Unfortunately Zunar is not the only cartoonist under attack simply for what they have drawn. Atena Farghadani is serving 12 years in prison in Iran. In 2011, the Syrian cartoonist Ali Farzat had his hands broken by Assad-supporting militia. And, of course, the artists who were murdered while working for the French magazine Charlie Hebdo are foremost in our minds again this week.

Nobody would suggest Mac might suffer a similar fate. But any call to censor a cartoon is an attack on free speech, and the thin end of a particularly unpleasant wedge.

Giving offence is part of the cartoonist’s armoury; it’s all part and parcel of democratic political debate. There is no right not to be offended, and we do nothing to champion free speech when we pick and choose who to support based on the colour of their politics.