So a few neons got eaten that is indeed life, and to nmonks bring on the leopard because I think that when you make a comment like that, it's what you would really like to do isn't it?
Of course not. The point is that an artificial situation in an aquarium in no way resembles the wild. If you think that, you're deluding yourself.
As for the cruelty of little glass boxes, you're absolutely right. In a perfect world, we'd keep fish in tanks the size of ponds or lakes or tide pools or whatever. But we don't. We can make rational judgements about levels of wrong though. If you keep fish and they breed, then you're basically giving them what they want. That's the benchmark used by professional aquarists and zookeepers.
You're also right about dead bloodworms having been alive sometime. No arguments from me. But from the point of view of science, a bloodworm is capable of less feeling of stress or pain than a neon tetra.
If you enjoy seeing one feeling animal harm or eat another feeling animal, then that's your pleasure. I prefer to minimise the harm my fishkeeping does. I research my fish before buying them, I optimise water conditions based on their natural ecology not what happens to come out of the mains water supply, and I don't feed live feeder fish.
There are very good practical reasons not to feed live feeder fish. Neon tetras, for example, carry neon tetra disease and false neon tetra disease, both of which affect a wider variety of fish than just neons, including something as un-neon-like angelfish and goldfish. The prime mode of transmission is when an infected neon is eaten by another fish, either whole or in part. Since neon tetra disease is incurable, and appears to be endemic to cheap, mass-farmed neons, allowing a predator fish to eat live neons is a very good way to infect that fish with an untreatable disease.
As a point of science, huge number of fish are not carnivores. Many cichlids (the largest family of fish) feed partly or entirely on algae and aufwuchs, for example. All the herrings and anchovies eat plankton, and the tangs and damsels all eat marine algae. Most of the small freshwater fish eat insects. Dedicated piscivores are relatively rare, for the same reasons than carnivorous mammals only make up a small proportion of the total mammalian diversity.
Cheers,
Neale
He has now turned his affections to the algae eater and male swordtail. My female betta who thinks she is rocky is still trying to have a go and steal his food. Think she is going to learn the hard way. 
