OK, I'll stick a couple of oars into these rather troubled and contentious waters...
Without wanting to "pick a side" here, I'll note that at a first skim-read of the paper (while on a train, so it really was skimming) I thought it bore many of the hallmarks of "advocacy research" in that it tried to give the appearence of impartiality while selecting cases and studies inclining, or trying to guide the reader, towards a pre-determined conclusion. One of the things which hit a bit close to home for me was the lack of discussion of a job I once had, a great many years ago, which was exterminating ferral pests on rural properties (and believe me, with some of the species introduced down here, and the damage they do and have done, "ferral" is a pretty strong indictment). Often using firearms because poison and other measures were too indiscriminate and so too likely to hit native, and certainly non-target, animals as badly (or worse) than the pests. Where does that fit in the "ethical" calculus of the paper? On a skim read, hardly at all. Any supplier of equipment I was likely to use would, as near as I can tell, be considered unethical. But for that purpose? Really?
(BTW, I wasn't doing it for fun - which it most certainly wasn't. I was doing it for the money, and not much of that. But I still think I was on the side of the angels rather than the devils when I did it. I'll also note that I've not owned a firearm since, nor shot at anything but targets - and then only on a handful of occasions. It's really not my thing. But I do hesitate before moving to condem. I also hesitate because I'm rather unsure that this is appropriate within the rules of the forum, at least anywhere but Ruffled Feathers and maybe not even there.)
...Mike
