Is it ignorant how people associate age with the ability to defend themselves in this case?

I had some people say a 20 year old man can't defend himself against a 56 year old and the 56 year old can rape him or beat him.

I think this is ridiculous because most 20 year olds I know are much fitter than the average 50 something year old. In most cases the 20 year old would beat up the 56 year old.

Is it ignorant how people associate age with the ability to defend themselves in this case?
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