The likelihood of serious accidents goes down, but it doesn't go down to zero.

So choosing a no-rules barred fight club versus a boxing ring is a matter of line drawing, and judgement calls.

Many people draw the line at no fighting at all, and call all boxers "stupid". Is that fair? And if it isn't, why is it fair for you to call Fight Clubbers stupid simply because they're willing to expose themselves to more risk than you?

Fight Club isn't a direct equivalent of Boxing/Muy Thai/etc. with merely added risk of injury.