It's true. Unless you ride DH you are not a cyclist. What was the first MTB race after all? Yes, the Repack, a downhill. Even those hippies in Marin County knew that the only reason to ride up a hill is so that you can ride back down it, and they were not above shuttling in the back of a truck.
Bushwacker, you also don't know how to do a proper call out/bet. You need to bait the callee properly, but you can't make the challenge seem too one-sided. Always understate your abilities or at least make yourself sound so ignorant that it will help to get people to take your bet. For example, in your call out, you might have wanted to try things like "My 10 mile time trial (at sea-level on a flat trail in Pennsylvania) when extrapolated over 100-miles clearly shows that I could complete the Leadville 100 in less than 8 hrs". Or you could say things like "I don't need to train for endurance because my pumptrack skills will help me to crush those roadie asshats".
So here is my callout. Come down to Highland Mtn and ride for a day. At the end of the day, if you can beat me down Hellion (without taking any wussy bailout lines), I will pay for your rental and lift ticket. You see, I am making this somewhat plausible, because you know that if it were on the first run you'd stand no chance. I am giving your youth, superior physical condition, cat-like agility and balance and youthful exuberance a chance against my 20 years of DH riding experience, Heck, I shouldn't even offer this bet as I'm pretty sure you'd beat me.
So to all of you roadie geeks and XC riding hippies, you are not cyclists! My way is the only way! Hasta La Vista!