Actually, we're only discouraging him from making a game that he will fail at! Trust me, spend some time on the forums and you will start to recognize those kind of projects! But instead of just saying "you can't do it" we are telling him what he can do, and what most of the beginners CAN do - make a small game. That's the way to do it!
It's like discouraging someone from jumping off a cliff - there is always a small possibility that he will survive, but nevertheless, it's not a smart idea.

Leonardo