why is that a problem?

Why does he think its his business?

Well I slept with my parents till I was 8 but we had a small house and it was fine.
Personally I'm against forcing kids to sleep separately but it'd be good to encourage him to have that level of independence

Does he sleep with you each night, or just in special situations, like after a nightmare ? My friends’ kids used to sleep with the two of them from time to time. The kids eventually outgrew it.

If they come in to you during the night, that’s one thing. But it’s not a good idea to encourage.
Sooner or later you all need your own space and it can be a hard thing for your child to deal with once you start insisting on it.

I slept beside my grandma until I was 10. There was really no extra space whenever she stayed with us.

My kids slept beside me a lot. Sometimes my daughter sleeps with me if she’s feeling sad, & she’s 13 now.

Tell your friend to mind his own business

You know what’s good for you and your son. He needs to shut up. Ask him to do so.

When my son was 5 he slept with me and I hugged him. The more comfort you give them the better for their mental development and emotional. Boys are still kids they also need warmth as much as little girls. And I never had a crib at all. My son slept with me from day one. No regrets

I think it's weird how little kids get put in a room on their own

No it’s ok

its not but i know people that will probably sleep with their children until they are 10 so
...

Sometimes even now when I go away for a girly trip with my mum and we can only get a hotel room with a double bed I have to sleep with her. I prefer to sleep on my own but near people. I used to go and sleep with my mum as a child if I couldn’t sleep and my dad was working away until almost my teens. I think it’s a good idea that you introduce your son to his own bed but if the nights he is anxious or wants to be close to you then tell him it’s fine for him to sleep with you.

That is OK. In a few years or if it ever starts to feel uncomfortable then it is time to move.

your guy friend is wrong

It’s none of his business.
You do what you feel is right when it comes to your child.