To be fair he never said 'I hate violence, war is horrible' IIRC he stated he realized what they (the first order) was doing was wrong.Finn being all like "All this violence, and war is horrible", then minutes later he's like "I got a light saber now! It's like I'm in the original trilogy. Hey Trooper that I used to work with, remember me? Stab mother fucker you're dead! Killing people is fun again!", was very odd.
Big difference