Well, you specifically said the Islamic invasions of Europe only bought, harmony, and prosperity.
Not what I said, and that book you cited actually does say there was much peace and prosperity in the peninsula into the "reconquista" (AKA Spanish Inquisition). Did slavery happen? Yes. But slavery was the norm in that world at the time. But how does that justify massacring people 300 years later in the middle east? It doesn't. It's just you trying to find moral equivalence.
If you didn't notice, I called out Western Europeans earlier as scum for attacking fellow Christians in the 4th Crusade.
European Christians attacked
everyone in the Middle East; Jews, Christians, Muslims...and they lost. Over and over. So I'm not sure why you would want to invoke them as the good guys when they weren't at all.
While the initial motives of the Crusades may have been just, in the end Western Europeans just seemed to go nuts looting, and shooting.
Their motives were never just. Just like how the motives of most Christians today aren't just. The motivation is the same for those people as it's always been; murder, pillage, rape...that's the Christian way.