Through online learning my son learned to do a lot of different accents and a really good general knowledge of different countries that add to his ability to do comic improv
I don't think anyone would question a person can learn things online. I think it is more a question of how big of a role that it should play. Your above example is a good one. He's learning something fun and applying to his life and that's a good thing. However, contrast learning accents to learning advanced foreign language or translation skills. Those sorts of skills would be difficult to develop online and time surfing from place to place may not be a good foundation for having the sort of focused persistence it takes to really learn a foreign language.
His interest in sociology and psychology which he learned about online were useful in dealing with feeling shunned in our community because he does musical theater instead of sports. When he has a problem he looks for solutions on his own online and it works really well for him.
And, this would be an example of something else that concerns me. It can be helpful to find support online and this board is an example of that. But there can also be a point where that focus can take away from in real life relationships and not all online support or information is helpful. To give an example there is a proliferation of anorexia how to groups online. Support groups can actually promote feelings of being misunderstood by outsiders. And, feeling some sense of online connection may take away the push to find in real life friendships which is something all people need. Surely not everyone in the town shuns your son for an interest in musical theater. If that was the case there would be no musical theater group.
