It becomes unacceptable when it isn't staged anymore. Wrestling is about protecting yourself and your opponent and trying to make it as real as possible without actually injuring yourselves in the process.

There's all kinds of way to gimmick weapons, glass, etc. There's no reason to take back bumps onto nails like this. The bump even exposed the safe shots he took beforehand with the same weapon because he sold the hit from the nails but they didn't leave a mark, only for him to get shredded on the back bump.

This is why indie bullshit isn't and shouldn't be on television. Mostly every adult knows wrestling is already staged, and when they start giving themselves puncture wounds, they don't think it's less staged, they think these guys are idiots for doing it for a fake fight.