To be fair, just look at all the people who have Chinese words written on them that say something that they weren't trying to say. How many of those people have had those tattoos for many years without ever learning that they were incorrect or fixing them?
I wouldn't go this route personally, but I know enough about tattoos to say with a high degree of confidence that many people just pick something out of the books on the day of the walk-in because they think it looks cool. I could totally believe this guy and his marine buddies said "that's a cool skull, let's get that".
It's like, how many people have Punisher stickers or t-shirts but have never read a comic book in their lives? Probably most of them...

Fair enough. Drunk 20-somethings military dudes getting a walk-in tattoo in some random country probably aren't going to be making many smart decisions. It was clearly not a well thought-out tattoo.
Nevertheless, I don't think the debate is about whether this guy got a bad tattoo or not, it's about whether he is a nazi or knowingly got a nazi tattoo.