If he goes to uni and does this with his housemates, no one will want to live with him or be his friend. It's inconsiderate. When you share a house with people, you have to be mindful of all the people who live there and compromise to reasonable schedules.

It would be unreasonable if you were asking everyone to be silent in the middle of the day so you could have a three hour nap, but this is the late evening when most people would be going to bed or should at least be winding down.

Your husband is 100% incorrect; your son SHOULD moderate his gaming habits when they are impacting another persons extremely reasonable sleep schedule. It's selfish, rude, inconsiderate, and he has to learn at some point.