Because the Nazi’s were all in on trying to portray themselves as descendants of the Vikings, upon whom they attributed a white supremacist philosophy that never existed. Going so far as inventing their own runes to mix in with Futhark, and also various icons that aren’t found in any Viking-age artifacts or described in the surviving writings. Modern-day white supremacists have continued this appropriation. So for certain kinds of imagery, a lot of people will just automatically assume you might be a white supremacist. A good tattoo shop should double-check requested elements, to make sure something doesn’t slip through, but as a client you definitely want to research everything you’re getting regardless of the shop.