Would someone who is a devoted weight-lifter be tough to fight even he didn't know any martial art?

Facing a bodybuilder may be daunting but if they have no fighting experience or more likely not to the same par as a martial artists. depending on the size of the bugger the martial artist should be able to dance circles around him. just don't let him get a hold of ya or your in for a world of pain, that in itself can be quite a challenge. any hit in the vital areas should be enuf to stop any1