I would say this is where you argument falls down. In the past Islam was only sucessful and "tolirent" in comparison to other cultures at the time. However while these cultures have developted and adapted Islam has stayed in the past.
It's not about Islam, but about Muslims.
See above, they were only in comparison to even worse things. Just because it was better than the others that were around at the time doesn't make it good.
It wasn't better, but the best, and it remain the same, and will be.