Now we know Picollo is able to destroy the moon at (or at least very near) the speed of light. Light takes 1.3 second from the Earth to the moon, Piccolo destroyed it in a second or two, but of course this counts the time for the light from the explosion to refract back to us from the moon, essentially meaning the time we see is the time for the beam to get to the moon and for the reflecting light to come back to earth
Now we see radditz dodge Picolo's signature light of death, a move as fast or likely even faster than the no name one he used to destroy the moon, since Piccolo was sure no one could doge this special move it must be his fastest.
Picoclo did not say he can't believe someone would be able to tank it or deflect it, he said he couldn't believe someone could be fast enough to dodge it, showing the emphasis is on speed.