I've heard hydraulic disc brakes give the best braking control w/o hardly any lock ups ever when used properly. Dunno about riding fixed on trails, sounds kind of ill fitting but whatever floats yer boat.

Back on topic though, try mentioning to said friend that you're doing trail maintanence some weekend and invite him along. It may open the door to explaining the whole deal about erosion and skidding and all that.

And btw, horseback riding causes a heck of a lot more erosion than a couple of skidding cyclists.

Peace.