Yeah, my opinion is a bit more pragmatic and attached to reality, where context, environment and your actions matter, not some "empirical" study done by universities.

Personally, I love my cats so I let them roam outside instead of keeping them inside like a prison. Then I also care about other animals so naturally they have a bell so they cannot (successfully) hunt other animals. But again, pragmatic approaches aren't for everyone, some people love books and/or data instead :)

The alternative to empiricism (science) is rationalism (wish-casting), not pragmatism (least harm).

I often let my dog off-leash. Weighing the risks & rewards, I pragmatically choose to break the law, knowing full well that I'm in the wrong, not some special case. I eat the tickets and social scorn without complaint. My dog has pretty good recall and is super gentle (esp w/ kids). But the big bad govt (and other parents) didn't write the laws with my special pooch in mind.

You're confident your cat doesn't harm birds. Terrific. It's still wrong, in the general case. So take your lumps.

A (huge) point in your favor is that 2/3rd of (domesticated) cats are feral. So keeping cats indoors in order to better protect birds seems quixotic.

In these parts, owners keep their cats indoors to protect them. Recently, my SO's cat escaped her "catio" and was swiftly caught by a coyote. (A neighbor saw it happen. Horrifying.) Maybe your locale doesn't have coyotes.

Edit: Another exception (that I can think of) is farm/barn cats. Pretty much a necessity. Alas, coyotes. And probably hawks.

Could be worth considering that outdoor cats in the US may actually be a positive because so many of our country's natural predators of rodents and birds have been wiped out.