You have to take the long view. Short term, you have to feel sorry for the Betta, but most of us think the damaging mutations are beautiful. The farms churn Bettas out in numbers you can't save. When I worked with importing, we once received a shipment of wild fish from Asia, and they had packed the spaces between the large bags with fancy Bettas, as living bubble wrap. They are that mass produced.
If you have room to take in 50,000 Bettas a week, you can talk rescue.
If we buy fancier and fancier fins, we get swimming pugs and French bulldogs - neat creatures but intentionally handicapped ones. It's a choice that will always be made. If I wanted another betta, I'd hunt for one with smaller fins and all the body colour I wanted. No one does that.
In order to have those fins undamaged (we don't like to 'adopt' Bettas with ragged fins) they can't be allowed to use those fins for swimming. They have to be jarred. They go into your tank physically unfit, with their noses up and tails dragging. In time, they get their muscles toned, but they are messed up creatures. Reduce the finnage by 40% and they become hardy community tank residents that swim well on day one. And they are still pretty.
The battle against cruel breeding is not going to be won by us. For every aquarist who decides Betta jarring and overbreeding are wrong, there are 10,000 who just buy. Balloon varieties of fish, blood parrot cichlids - we shape fish for convenience and because cute sells.
