In a way he's right. Assuming he wasn't lying, he's saying that if he didn't do what he did then all of the Kang's would've destroyed every universe and there would be no more people. It's a solution that does work but he is still killing people all the time by pruning the branches. The thing he either didn't consider or chose not to do(which would definitely make him a villain)is why not just kill the all the Kang variants? Supposedly it was them directly that was waging the multiversal war so if he just kills all of them and not try to conquer other universes then we could've had a healthy multiverse the whole time. Or he could also kill himself at the end and eliminate all the Kang's thus protecting the multiverse from a war.