It can burn diamond at 720 °C, what do you think it’ll do to soft tissue over the course of an entire lifetime. Things helping aerobic life survive are
a) partially consisting of partially oxidized polymers in the form of carbohydrates (remember, the only thing that cannot burn is what has already been burned);
b) oxygen’s peculiar, natural triplet state which greatly slows down its kinetics compared e.g. to its horrible relative, ozone.