I don't think he defended Islam. I think he defended the right of individuals to be Muslim,
Well that's a straw man because, as far as I recall, that has generally not been the position of posters here. What I remember mostly was Slim being critical of the very idea that Islam was even being discussed in a negative light. He would not engage in such conversations but rather summarily dismiss them outright as bigoted, xenophobic, whatever, which is patently absurd.
and not face persecution.
How is persecution being defined here? Drawing Muhammad? Criticizing child marriage? Criticizing a culture of misogyny and intolerance of homosexuality? Pointing out bad ideas and backward customs is not persecution. Criticism notwithstanding, the truth of the matter is that western countries have bent over backwards to accommodate the practice of Islam.
I think he found Christianity and Islam equally stupid and anachronistic to a modern liberal democratic society.
You can say the same about all religions. The point is that Islam is more violent and intolerant than other religions. There's a reason Hinduism, Buddhism, et al., are not dominating the world's conversation on terrorism.
Where I disagree with his view is this: Christainity (except perhaps in dumb places like some African states and the American heartland) has come into cultural equilibrium with science, reason and Liberalism. Some Muslims have also entered this equilibrium. I have met many such people. Other Muslims seems to see Islam as above history and culture, instead of part of those, and that's where I have a problem. A lot of them see history as insh'Allah, pointless to try to change, which is why so many allow themsleves to be ruled by despots.
This is what I always argue, of course. There will always be moderates in any religion but Islam generally speaking is a tougher nut to crack because of the totalitarian nature of its text which is considered to be the final, inerrant word of Allah to humanity.