This is not about intolerance or caused by advancing age (I had similar opinions at 19): I am dumbfounded (with the emphasis on dumb, 'cause I don't get it). Don't get me wrong: people can to whatever they want, as long as it does not affect me. But...
I cannot understand--never have, never will--why anyone would want to pierce his or her skin with metal things. Nature did a fairly good job making humans. At no point in evolution was metal part of anatomy (at least there's no fossil evidence, but I will go out on a limb and assume). Also, I can't think of any fauna or flora with metal bits, for that matter. I am not even in favor of piercing ears, but understand the necessity for jewelry sales. It's the economy, stupid...
If people do it to aggravate others (people like me), then they are completely stupid. There are easier methods, which do not require suffering pain.
If people do it for (alleged) pleasure, there must be a better trade-off for 1 second of pleasure in return for 23 hours, 59 minutes, and 59 seconds of discomfort.
If people do this to "express" themselves, there are easier methods.
Less disturbing, but equally inexplicable is the growing prevalence tattoos. They are more like a blemish and do not increase attractiveness. Women take note: I noticed a headline recently that the majority of men do not find them appealing.
Marking of skin with ink may be acceptable--even necessary--in primitive cultures, which do not enjoy having brand logos to reveal a person's personality or the benefit of Facebook to communicate one's salient traits.