Considering that the biggest part of that particular punishment is supposed to be keeping you away from your friends, I guess the joke's on him? But seriously, what does he hope to achieve by doing this? 'Oh, that'll teach my kid, bet they're gonna go out and look for friends right away. Oh wait, they can't, because I just forced them to stay at home. Still, I am reasonably certain this helps somehow.'

Seems like we're missing huge chunks of info here.

Isn't it the same as if you would told a fish to stay in aquarium?

You don't have friends, so he grounds you, meaning that you can't even go out to make friends... Seems legit.

He wants you to make some imaginary ones.

i am now your friend problem solved

Seems pretty counterintuitive lol

See now you have friends :)

Yes, confine your child to the house to fix that problem

But why ground you? It's not like you have anywhere to go