They are.  Lasers in the movie, are essentially laser in real life.  If they are going to base something off of real life, they are going to have to adhere to the rules surrounding it.  If they use a laser, it would have to go at the speed of light.  Also, we do not know what is inside the guns, so there could be a device to alter the light rays, and make the beam visible for a short time.  We really don't know what technology they use for their devices, but I still say that the lasers travel at the speed of light.  The only complaint I have is WHAT'S WITH THE EXPLOSIONS IN SPACE??  There is no oxygen, and explosions are gouts of flame.  Flames need oxygen or there are none in the first place.  So why do they use explosions in space?  It just doesn't seem to make sense.  Sure it adds to the pyrotechnic display, but they could find so many other places to insert that, so why mostly in space? 
Anyways, that's just my two cents.