That is just plain stupid there is not enough metal to cause an issue.
An yes nipple rings are also stupid.
On the contrary, there are some huge (3+ inch diameter) nipple shield piercings in tribal designs that look like razor blades. And nipple rings that are designed to look like daggers and cutting tools.
Also, I hope some Hollywood writer hears of this case and writes it into the next terrorist plane hijack movie.
Some nipple rings are quite large.