I'd have no problem with it really... currently on my street (about 3 blocks long) there is a Rabbi, a Baptist minister, two Islamic scholars (from UofT), party members from all the politcal parties in my riding... all in all each person is respectful of each other's beliefs and values, and they don't seek to impose them on each other... in fact there has been some interesting debates at some dinners.
The way I look at Cat Stevens is about as much of a threat as any "celebrity" that is devoted to there faith... yes everything they say is scrutinized and sometimes they make mistakes - I tend to judge people more by their actions and not their statements, Cat Stevens has supported numerous charities (both Islamic and otherwise) that do a great deal of aid through out the UK and even here in Canada... unfortunately some of his aid has reached radicals of his faith; much as I'm sure that some of my donations or work as unfortunately benifited radicals of mine... its all realtive.
Oh yeah... besides I'm a fan of some of his music