He's obviously trying to engage you in the same activities that he's doing, seeking active companionship in leui of more passive interaction. This has been going on for a while If he feels the need to express his discontent by claims of your activities indirectly aggravating him. An easy way to dissolve his mock credibility would be to simply surf the Internet in another room, but that doesn't address the roots of his inability to abide your actions.
He knows his qualms hold no real water and he's redirecting attention to a more tangible concern in hopes of you subtly addressing the issue. This stems from a fear of being embarrassed as he still values your opinion of him and he'd rather you see him as an aggravator then appeal to your relationship.
How you deal with the problem is up to you. Personally I'd tell him to shut the fuck up and stop being such a fucking pussy about expressing himself, but I have the advantage of years of dealing with pussyfooting motherfuckers.
Hanging out with my friends in similar situations usually leads to an unsaid agreement that anyone can come and go at their leave, and do whatever the fuck they want in the meantime. I'm not a fan of being obligated to do anything so that's just the way I like it.