Do Pokemon even need a Pokemon rights group? They're smart enough to form their own if they felt the need to, but they apparently are fine with things the way they are (Mewtwo aside, he seems to be the only one angsty enough to want to form said group). Pokemon don't have 1:1 needs or values that humans have, much like animals. Plus, they get to live more or less the way they want, so I don't feel like they'd really need our intervention.
The difference between Pokemon and animals in this situation is that an animal tends to only act instinctively. A Pokemon will actually think things out, unless it has a brash personality. If they really felt like some kind of danger was escalating, they'd put two and two together and just leave the area. They don't have to worry about looking for a new household or not having the means to move right away, they live off the land.
In a way, you'd think it would be sort of dangerous to have the beasts around that have the instincts of animals, but the intellgence of at least barely functioning humans (Slowpoke, for example, and probably at best geniuses, but this is probably reserved for Pokemon like Alakazam and Dragonite). But by and large, they seem to be either benevolent, or removed from humans enough to not really care to mess with us as long as we give them the same kind of respect. They have better things to do with their time, just like most of us iRL don't spend all day thinking about animals, unless that's your profession.
At the end of the day, humans, monsters, and animals all need to be treated with respect and just leave each other alone most of the time. Even animals aren't nearly as defenseless as the picture those animal shelter commercials paint. Most of that came from human intervention and mistreatment to begin with. The difference is that there are some animals that can't function too well without humans anymore, such a dogs. Pokemon seem like they could really live off in their own little world/paradise forever and be okay. However, I'm sure some of them would miss humans, like I'm sure some of us would miss them if we just completely separated like that.
So in short, no, a Pokemon rights group isn't necessary, because they're absolutely capable of handling everything, barring surprise attacks, themselves. Frankly, we can't handle surprise attacks either. I think some of us just want to feel like they need us in the same way we want to feel like animals need us. It's sort of a selfish but human way of thinking.
As far why Pokemon willingly battle for humans, that's merely an obedience thing. Pokemon don't do evil things, they just obey their commands, as Ekans put it in a very early episode of Pokemon. Though even that's debatable as Meowth didn't seem to agree. But, like humans, that probably depends on upbringing. Meowth felt like he was dealt a bad hand in life, so it probably warped his judgment, but maybe that's his fault for wanting to be more human. I could go on and on.
Interesting that I'm the only one to reply to this topic. :P I guess it's hard to imagine considering the games never bring the idea up at all. That, and the trainer games are such a decidedly human perspective on the entirety of the Pokemon world, and it's hard for us to relate to anything that isn't also human.
