Your buddy is smart.
In a panic stop, most noobs stomp on the rear brake to stop (instinct from cars). He's trying to get you to react using the front brake. Takes practice to map the muscles to do it.
Rear brake-only isn't so bad straight on - just lousey stopping distance (front brake has 3x the stopping power of the back), but in a curve, it's a problem. It puts a force on the bike that stands the bike upright and you'll go wide in a turn.
Best example I have was sitting at a light about to enter my secret, nearly empty, tight twisty road and the latest sportbike pulls up with a guy in new leathers. "This road good? Can I follow?" Sure.
Half mile of twisties later, he's not in the mirrors; I stop, wait a sec and spin around. A few curves back, he's dragging his bike out of the woods outside the apex of a tight right hander, physically OK - he'd just missed a couple of trees. He had leaves and crap stuck to his helmet, leathers and bike and the bars, pegs, fairing, tank were all tweaked, but the bike was rideable. It was a slow turn and he locked up the rear, stood it up, and went straight through it.
(We got it started, about the same time he got angry with me(!) for 'going so fast' or some crap like that. He was OK and I wasn't going to put up with that BS; fare thee well!).
Long answer, but your bud is right; learn to rely on the front brake instinctively, then add the rear later.
- Charlie