Do you eat the mosquitos or ticks that you kill? If a mouse or a roach moves into your house, do you leave it alone or do you kill it and eat it? Do you eat the dandelions in your yard after you put down some weed killer?
We kill carp. Lots of them. It's fun and we don't apologize for doing it. Nor should we. And since when are we not supposed to have fun in our outdoor pursuits? Would you be okay with bowfishing if we only frowned when we did it??
It has been proven many times over that common carp are destructive, invasive species and that killing them is a good for our lakes and rivers. No need to be grim about it.
http://www.carpbusters.com/documents/9_1_06_CT_art_.pdf (I could post dozens of 'carp are destructive' research papers here)
If you don't want to bowfish, then don't do it. But don't come on here telling us we are unethical.
We are the ones helping out the waterways.