I also did not drink until I was 21, and went straight in for stouts and porters. I think they are in some ways a good start because the roasted malts are kind of sweet/chocolaty.
I still prefer them, plus all other ales (English especially) and over time a taste for IPA. Never got a taste for lagers or light beers.
So I would say get a mix from a good brewery (like Bell's from Michigan, Left Hand or Sierra Nevada, can get all at HyVee) and get some Pale Ale, IPA, Brown Ale, Stout, Porter and then can taste test. Then he can learn about hoppy vs malty, etc.
I still prefer them, plus all other ales (English especially) and over time a taste for IPA. Never got a taste for lagers or light beers.
So I would say get a mix from a good brewery (like Bell's from Michigan, Left Hand or Sierra Nevada, can get all at HyVee) and get some Pale Ale, IPA, Brown Ale, Stout, Porter and then can taste test. Then he can learn about hoppy vs malty, etc.