European colonialism. Take a look at Wikipedia's article on Muslim-colonized Spain, and it's almost nothing but praise. The entire opening section doesn't even mention the slavery of non-Muslims that was practiced.

Under the Caliphate of Córdoba, al-Andalus was a center of learning, and the city of Córdoba, the second largest in Europe, became one of the leading cultural and economic centers throughout the Mediterranean Basin, Europe, and the Islamic world. - https://en.wikipedia.org/wiki/Al-Andalus