Unsolicited advice is worth less than you pay for it. I've had a bunch on run-ins with people offering advice that I don't need (usually about sailboats, not bicycles) and it is almost always crap. I try to smile, wave, say "thanks", take a moment to consider their advice, and almost always (very much like you did) disregard it as crap.

As others have said, the front brake is the one that provides the bulk of your braking power, and the rear is mostly useful as a backup for front brake/wheel failure or for very slippery or bumpy terrain.