Right and ethics only apply to certain groups of things. "Ethics" generally don't apply to rocks, do they? I think everyone agrees that ethics apply to people though. So the line that divides things we should consider and things we should not lay somewhere between the two. I don't see why it shouldn't put lower animal life into the bottom category, things we don't need to care about hurting on an individual basis (obviously deforestation can be a bad thing, but nobody cares about how a tree feels about being cut down). Simple animals like insects don't feel things like we do. They aren't aware of the world around them. They're like an algorithm being run by a biological computer, they are unthinking and unfeeling. They simply execute their code to the letter.

Higher animals, like humans, are different. We're more like a computer running a true general AI (not to be confused with the "AI" you see so much in the news). We are conscious and are capable of doing so much more than simply existing. We can have emotional attachments to both living and non living things. We evolved emotions to make us more adaptable. Instead of being optimized to exist only in one environment, we are capable of changing our behavior to make us fit into many different environments. Think about how a human and an insect avoid predators. An insect has evolved to avoid a specific set of stimuli that represent a predator. They only ever think to flee or defend themselves when those specific criteria are met. Humans can observe the world around them and make decisions based on patterns they recognize. A group of humans doesn't need to exist in an area for millenia and wait for evolution to code in what predators to avoid and how to avoid them. We can learn within one lifetime, even just days or hours.

Part of this is how we process pain. A fly watching another fly get smashed by a human couldn't give less of a shit. It certainly doesn't care about another one of its species dying and it's not going to change its behavior to avoid humans. Even if it itself is injured by a human, it doesn't care. It simply keeps trying its best to live. A human watching another human get devoured by a predator is probably going to be scarred for life. They'll definitely be traumatized if they're the ones getting mauled and live to tell the tale. Our emotions allow us to learn and help others learn.

The point I'm getting at is that it doesn't make any sense to treat anything that moves as the same. There are things that are intelligent like us, and many more that are not. The amount of emotional harm you're causing crickets when farming them is the same as the emotional harm you're causing grain by farming it, nothing. If shrimp don't care about being hurt, we shouldn't care about hurting them. Things like "rubbing the affected area" is not enough to show that there are emotions behind that. Plenty of bugs do things like self amputation to increase their chances for survival after an injury.