Personally I don't think that the cover (or the use of the prophet, or any other religious figure in general) in a satirical way is racist.
There is a difference between racism and criticising/lampooning (publicly criticize (someone or something) by using ridicule, irony, or sarcasm.) religion.
Islam is not exempt from satire, just like Christianity/Judaism/Buddhism aren't either.
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What are your thoughts on the satirisation of Mohammed (and why it's any different that previous covers satirising Jesus/Virgin Mary etc)?