Taking pleasure in killing them is.
I shoot rodents, pests, etc... all the time and I get satisfaction from doing so. Pleasure? No. Satisfaction? Absolutely.
I've shot pigeons from farms, churches, school areas, stores, etc... that were nothing more than filthy pests, and have no issues with doing so, nor do I have any issues with anybody else doing so. The pigeon shoots in question in Pennsylvania, though, are far from that IMO. They may try to loosely justify it under the guise of killing pests, but those birds are either trapped in big cities (and could have been disposed of in many other ways) or raised for this purpose. They are then propelled out of launchers to be shot by the "hunters". I do agree this is overwhelmingly an example of just killing them for pleasure. I doubt very seriously that anybody in attendance is there from some compelling need to assist in fighting a pest problem.
That said, it's been often said on here that the people who do this are also the people that have no problems killing people......or are likely to be serial killers, etc. That's bs. The people out shooting those pigeons are just inconsiderate, lazy slobs out having their "good time". I doubt most of them have the interest, balls, desire, or motivation to be killing humans indiscriminately.