Good friend, bad GM/Player, what would you do?

[Wuzza]

Railroading is the WORSE thing a DM can do. :(

Obvious railroading is the worse thing a DM can do. A good DM can railroad a party without them knowing.

The problem is that as a player, he is terrible, lacking any ideas and always failing to get the most obvious clues, portraying all his characters the same way and always confronting the rest of the party because his character always wants to take another course of action (which most of the time is the dumbest one).

The only bad thing in this paragraph I can see is "always wants to take another course of action". As long as he's having fun, I cant see the rest disrupting play. Maybe just broach this subject?

Some people, even with the best of intentions, just aren't good DM's