Yes. Gorillas fall out of trees and beat each other silly all day, every day and it doesn't affect them at all. Yup.
Has it ever occured to you that gorillas can easily hurt each other very badly indeed, when they actually try? Or that even the minor altercations between gorillas we see on Youtube cause more damage to those involved than we realize? That an animal doesn't act hurt doesn't mean it isn't. First law of the jungle: Never show weakness.
If you maintain gorillas are nigh impervious to damage, provide sources. Show us a video clip of a silverback being hit by a car and shrugging it off, or being involved in a serious fight with another gorilla without taking a scratch, or anything that would indicate actual physical combat is not something that every gorilla try to avoid for the simple reason that it is very dangerous to them.