If you have to make a focused effort to be more peaceful, to acquire peacful behavor, then a state of peace is not natural.
In a lot of human behavior, the more you express it, the more easily it is expressed in the future. I guess your sense of what "natural" means would suggest things of this variety become more natural the more you practice them. Are you suggesting that people who tend toward more aggressive behavior shouldn't try to change what is more "natural" for them to express?
So I guess the point isn't about whether it's natural or not, so much as what will lead to a happier tomorrow. Punative measures don't always seem to be the best answer to that.
Without struggle there is no growth.
I took struggle here to mean conflict, but I could certainly be wrong in that guess.