Destroying planets can be hazardous to your health, that's a given. The only way to avoid any damage is to destroy the flying chunks of planet that break off after having been zapped by your laser missile guns!
Save your own planet from destruction by ridding outer-space of these maniacal lumps of space junk.
But remember, being trigger-happy can only get you so far. Try timing your missiles to coincide with the trajectory for maximum effect!