Same reason an alcoholic needs alcohol to keep from shaking, you're addicted. Go ahead, try to stop. You'll shake just like they do.

There are anaerobic bacteria that don't need oxygen to survive. That was the norm before The Great Oxidation Event when cyanobacteria started releasing oxygen into the atmosphere during photosynthesis. Prior to that there was very little oxygen in the atmosphere, and anaerobic bacteria ruled the world.

After the GOE the high concentration of oxygen killed off most of the anaerobic bacteria, and what was left were organisms that made a blood truce with oxygen. Aerobic organisms gained incredible power from utilizing oxygen for metabolism, but eventually die from the accumulated damage the oxygen does to them.

The short version is that life needs something that's at least a little unstable in order to extract chemical energy from things.

The post is correct when viewed in a particular light, on a technicality, if you squint. By that same technicality iron rusting is also burning very slowly. They're ignoring the rapidity which is implied by "burning". But yes, oxygen is unstable, oxygen helps burn things, and oxygen is toxic if you get too much at once. Though you'd need to be breathing pure oxygen pressurized to about 1.4 atmospheres, or regular air pressurized to about 7 atmospheres, for that last one to happen. It's a legitimate concern for deep SCUBA divers.

But why does life need instability? Chemical instability is, in basic terms, just stored chemical energy, and that energy wants to be released. The more reactive something is the easier it is to get energy from reactions involving it. There's a balancing act here where more reactive means easier energy, but also more dangerous. Oxygen is in a kind of sweet spot where it's stable enough that it's not generally going to explode or catch fire on its own, but can be coaxed into doing those things in controlled ways with other chemicals to extract energy when needed.

Because our atmosphere is full of oxygen and nitrogen. Oxygen happened to be the chosen option for some reason, probably because nitrogen might not be reactive enough, idk I'm not a biologist or a chemist forget what i said

Organisms need some oxidizing agent to respire. We use oxygen because it's very highly reactive and thanks to photosynthesis is goddamn everywhere.

https://en.m.wikipedia.org/wiki/Adenosine_triphosphate