The thing with boxing is that that's two people voluntarily fighting without someone else telling them to.
Considering that pokemon and human were much more equal in the distant past, it does look kinda similar to the Falmer-situation in Skyrim (altho the circumstances aren't the same).
Two more or less equally-sentient species lived together, then one invented the means to more or less enslave the other, and now the other species (the pokemon) have sort of ended up getting stunted/stuck at their current stage whereas humans have gone on to be all modern and intelligent and stuff. While also using the "lesser" species for everything from food to warfare and whatever you can fit in between.
The old tales in the library of Canalave city seem to suggest humans and pokemon were equal enough to understand a common language at one point.
There's also mentions of humans eating pokemon. And censored in translation, humans and pokemon would marry each other.
It also makes the whole "hand out dangerous elemental creatures to children and encourage them to head out and battle and stuff" make a lot more sense, as they'll just grow up and accept and enjoy it as a normal everyday thing without really overthinking it too much.
Pokemon have proven themselves to be way more intelligent than most people believe (just look at Meowth of Team Rocket. It's just a regular Meowth who on it's own learned how to walk and talk like a human. If he could do that, then it wouldn't surprise me if others could too.)
All these years of things being this way has probably just conditioned the pokemon to view battling and getting beat up and bruised as a good thing.
The pokeballs probably mess with their heads too.
I mean, just look at the PMD-games.
No humans in sight anywhere, and those 'mons are way more advanced (they have peaceful societies (as the games always explain that the pokemon in the dungeons aren't necessarily all-bad, it's just something about the place that makes them upset and violent), send their young ones to school, know how to create fabrics and medicine and how to operate more complex devices, and so on) than the ones in the main series games.
The first PMD-games have some ruined seemingly man-made structures around (the decrepit lab), which suggests that there used to be humans around but something happened to them.
And now that they're gone, wild pokemon no longer have to live in fear and constantly be on the alert to defend themselves or their kin, so they've started to advance as a species again because they're finally free.
In short, TEAM PLASMA WAS RIGHT!!!!
Actually no that's just a joke. >->
That's just my head-canon and stuff tho.
I love stuff that's got an innocent outwards appearance but that's actually pretty sinister if you scratch the surface.