I have arrived, with science.

If Mason doesn't feel fear (Or much of it, anyway) he'd be defying his inner..wolf..y..ness..Lemme explain.

Organisms survive and thrive because of their survival instincts. Self preservation is a thing instilled in all (most) living things, by use of pain and fear. These instincts are what allow them to assess a threat, and develop a flight or fight response. That's when the adrenaline is pumped through their body, to give them added strength and heightened senses. So without fear, you would be:

A) Missing out on adrenaline boosts, as well as many of Mason's survival instincts as a human/werewolf/hybrid thingie.

B) Totally and completely oblivious to threats until they caused you pain. Perhaps even if they do cause pain. This would be especially dangerous when he's an out of control werewolf, because Wolf would basically bumble around and break stuff while totally unaware of any danger he might be in.

THEREFORE. It is my observation that fear is a good thing, and that it would be in your best interest to allow Mason to feel fear. Also, it begs the question: Why doesn't he feel fear? Is it an emotional thing, as in his conscious mind constantly keeps the fear at bay? (This would mean that he could still be affected by fear toxins and yellow lanterns, since they go to the sub conscious mind. This would also explain how he could steel himself against the bat glare.) Or does his mind physically not give off the stimuli for fear? (Which would have to be attributed to some strange mutation or disease in his brain.)