Do you feel bad about killing a fly?

I feel about 5% bad when I kill a house fly, 95% like a hunter who has conquered her quest.

My boyfriend can't stand the idea of killing a fly, and will try to catch them so he can release them outside.

I understand the merits of "wouldn't harm a fly" but I mean, come on. The fly is dying if you put it outside in the cold! I have little remorse for killing a fly and now I'm wondering if that makes me Yellowstone-ready (ranchers have to make tough decisions out there) or a ruthless killer.