No one is saying the Ottoman Empire itself was idyllic but keep in mind it spanned almost 600 years and towards the end was quite decadent and degenerate. Many of it's practices need to be taken in context with the world at the time and most slavery is ethnically motivated.
In terms of religion, the Ottoman Empire was far more tolerant then the countries of "Christendom":
That's not a fair comparison, for you're comparing a single government, one devoted to empire, with more than a score of Christian national governments, whose particular aims may have been different. However, if you compare the Ottoman Empire to another Empire, say with the Roman Empire, I think you'll see that there's not that much difference in institutional tolerance to other people's faiths and culture. Why? Because Empire's must assimilate the people's they conquer, or must maintain a constant garrison over the conquered populace. Obviously, it's in their interest to be tolerant and even-handed.