Bo Jackson -- Defends Lance Armstrong ... 'Nobody Is Perfect'

Lance Armstrong has a very powerful ally ... perhaps the GREATEST ATHLETE, ever ... Bo Jackson ... who tells TMZ Sports he still believes the disgraced cyclist is a good guy.

We spoke with Jackson ... who tells us he's been friends with Lance for years -- and despite his misdeeds, Bo is convinced he's a good person.

"Lance isn't perfect," Bo says ... "Nobody is perfect. The only perfect man was nailed to the cross."

That's why Bo says he wasn't surprised when Lance agreed to ride in his annual Bo Bikes Bama charity event on May 2nd ... telling us, "This man is doing something out of the goodness of his heart."

"Lance is the godfather of cycling in my book. If he wants to ride in my charity ride, I'm not going to say no. I'm trying to do something for my people in Alabama."

One last thing ... since Bo is an avid cyclist (and one hell of an athlete) we had to ask if he thought he could keep up with Lance on the bike. Bo's response: