Technically, the most positive possible strategy against an aggressor is Tit 4 Tat plus 10% random forgiveness. You never start the shit, but when someone else does, you hit back hard 90% of the time. The person that starts shit will always come out worse by a small margin in this scenario, but it still means a shitty downward spiral for up to 90% of the time.

Oh no! Replying to this person is appeasing them