Not all priests are like that.
The Catholic Church has been around nearly 2000 years.
And most wars are caused by the greed and selfish needs of leaders and use religion as a means to fan the flame of wars. A truly religious person would not lift a hand against another. You think the Crusades were to spread the Word of God by war? No. Jerusalem had a lot of wealth a knowledge. In fact, after the Europeans had conquered Jerusalem, it was there that they discovered higher mathematics(from the Greeks and Romans) that helped Europe out of the Dark Ages. They also got advanced medicine from the Arabs.
Many historians agree that if not for the Crusades, Europe would not have advanced.
Also, remember that Attilla, Khan, Hitler, Pol Pot (look him up), Lenin, Stalin waged war and mass murder without religious means.
BTW, Catholicism is Christianity. Catholics worship Jesus. Priests used to be able to marry about 500 years ago until a Pope changed everything.