There is some good in it though. We aren’t completely honest if we outright dismiss everything. In christianity, unlike normal mercenary ventures, the crusades had the benefit of logistical support, including financial backing, hospitals, food supplies, and a justification for whatever brutality you had to do when looting and conquering. While as a knight or a lord. You could spend your peasants in this war. They would be awarded with heaven (nothing). While you gain lands, plunder and prestige. It is like a wealth transfer this way. By grinding down lives to empower yourself. Too many peasants? Grind them down in a war for more lands, loot and control. Like the wars for «liberalism/freedom» in the middle east today. Where the military industrial complex can enrich itself on tax money.
While islam allowed for a legalized extortion racket. They perfected the concept of structured plundering through systems like jizya and ghazw (organized raids against non-believers). Islam is the proto corporate empire.
It would be beneficial during certain times in history to be a part of it.