Another question about territorial aggression in dogs, was I right to stand my ground and fight as long as it wasn't too bad or should I have just backed off immediately?

I thought at the time my brother’s 11 month old Golden Retriever was just showing me who was boss so I stood my ground to show him it was me. In hindsight I missed way too many signals and I’m lucky to only come out of it with a lot of bruises. He displayed all the signs of territorial aggression. He backed down this time but was that the right course of action to take? He normally plays rough with me, but this one was different. But if let him win doesn’t it reinforce his behavior? (See my question from Monday for more details). I’m finding squat on the web and his trainer was clueless. Reassuring.