Topic remains under debate, with strong arguments on either side. Lateral movement makes you harder to hit, but also makes it harder to get a center hit on the other guy. Standing still improves your hit potential, but also his.
Often, the situation will dictate: i.e., nowhere for the shooter to move. Best to know how to do both and be ready for whatever the situation demands. However, basing a strategy on the presumption that the opponent can't shoot is never a good idea.