Secondly, I would point out that there is no credible evidence that Muslims engaged in the genocide of peoples, rather, their form of hegemony was either slavery or taxation. In terms of slavery, it was more complicated and nuanced than Western slavery and some slaves were actually granted elitist positions within the state and were treated better than the common person.

Thirdly, I would point out that no Islamic hegemony exists today so its not relevant whereas American hegemony exists today and it is the cause of suffering for a lot of people.

Fourthly, I would point out that Islamic political theory never posited the values that were espoused by Western liberal theorists and thus, its not contradictory for them to treat people in a certain way whereas the preaching of liberal values has been done in an hypocritical manner throughout history.

Fifthly, I would point out that the proper comparison is not between Islamic states in the past and contemporary political regimes, but rather, Islamic states in the past and non-Muslim states in the past such as India (pre-Islam), China, and Europe.

Also, see my previous post here on these types of issues:

http://jinnzaman.hadithuna.com/part-iii-islam-and-empire/

hope that helps.