Ditto for nose, tongue, eyebrow, and all other visible piercings; frosted hair on men that sticks straight upward; slovenly habits and jive-like attitudes; etc.
Ted Kennedy and his ilk can pass all the job protection laws they want but no one (except Starbucks) will hire people whose appearance conveys a poor work attitude, or a selfish "What does my company do for me?" attitude.
This is not a new problem, but a different flavor on an old problem. Remember that the basis for IBM's ("Big Blue") dress code (blue pinstriped suits) was to de-emphasize a person's individualness while on the job. It's not new knowledge that the best employees are the ones who aren't trying to push the boundaries while working.
Being tattooed or pierced does not necessarily imply that anyone is trying to push any boundary at work. That said, if the person removes the piercing(s) and can cover the tattoos with clothes at work, where is the problem?