You say that now because you don't believe it's possible for someone to capture a large enough quantity of oxygen to impact you.
If that were to change, which it may, you would feel differently.
If that were to change, which it may, you would feel differently.
It's a fact that, right now, the dude can use whatever amount of air he feels is appropriate for his circumstances. Even if I wanted to interfere I doubt I'm even on the same continent as he is, and it isn't my business anyway.