There’s no one Muslim empire so you’ll need to be more specific.

All of them, quite literally.

“normal” levels of mass killings and rapes

No such thing as “normal” levels of mass killings and rape.

My whole argument is that not all societies have committed crimes as terrible as those committed by 19th-20th century colonial powers.

My argument is that all societies have these things in their history. Not the goalpost of my argument.

the Uighur genocide is downright peanuts

Wow. It’s genocide. Period.

Nope, that’s America. Britain is third IIRC.

Point stands, regardless if that’s true or not. Britain is still neocolonial.

Syria, Afghanistan or Nepal

Syria and Afghanistan were both part of the Muslim empire.