Before 1999 he was never more than a decent one-day rider. He certainly showed no grand tour winning potential.
Besides, there aren't mutiple teammates who have declared that there is systematic doping in the Jamaica sprint team. The number of teammates who have spoken about systematic doping on the US Postal is growing quickly.
Finally, Bolt is a likable character, whereas Armstrong is extremely vindictive towards anyone who publicly dares to question his myth.