The answer is, unfortunately: It Depends. There are indeed people who will judge you on a tat or piercing or other body mod, just as there are people who will judge you if you come to work in ripped jeans and a T-shirt with three different colors of housepaint and a layer of cat fur. This tends to be less of an issue in places where you either aren't dealing with customers who might react badly, or are expected to be a bit eccentric; academia and "research" types can get away with more than folks in the main line of business can, and sales personnel are generally expected to be well-turned-out but otherwise non-distracting so the customer can concentrate on the transaction.
If it isn't something that's displayed during the interview or at work, it's unlikely to ever be an issue. If you want it more visible, you are gambling. It's not a major risk, but don't assume it's 100% harmless.
And of course a tat which implies you're involved with anything resembling a violent or hateful group is likely to get you invited to interview elsewhere.
Basically: Don't be stupid. If you do it, get something tasteful, don't shove it in people's faces and force them to react when they'd really rather not deal with it, and for gods' sake don't get a tat until you've wanted the same design for at least a full year. (If in any doubt, friends who do skin art tell me, consider a temporary and see if you keep buying and re-applying it.)