I encourage everybody to at least glance through the wikipedia article on the subject just to have an idea of just how many cultures have used the symbol:
http://en.wikipedia.org/wiki/Swastika
Speaking from an artist's standpoint, it's actually a very beautiful shape, a straight-edged version of a spiral sun. I can see why so many cultures have used it. I can also see why it is still used today in many cultures.
Yet I also sympathize. Understand that this is not just a Jewish issue. Hitler killed so many more groups of people than that. Romanians, Slavic, Polish, Homosexuals, Disabled, those of non-european descent, political enemies, even Freemasons! You also don't need to be part of that group to be sensitive to it. Because of the horrible, horrible persecution which happened and the aftershocks of it that still exist, in Western culture, we still associate that symbol with the political movement. When we see it, do we think of Nazis or do we think of well-being? I, personally, think of Nazis. I can't speak for the rest of you. In the case of the jewelry shop, I'm sure they have great intent. I'm sure they're not selling to Nazis, but instead to new-age folk (I highly doubt to Hindus/Buddhists/Tantrists, but I may be wrong).
In order to understand those reactions, you need to look at why they're "oversensitive." Are there militant groups out there right now that are actively anti-Jewish and use the swastika as a political symbol? Yes. Are there groups out there right now that make accusations of Zionism and have in fact threatened war with an entire group of those of Jewish descent? Yes. It's absolutely understandable to me that they would be shocked and react very badly to seeing what they would automatically perceive as Nazi jewelry. If I walked into a store, that would be my automatic assumption as well. I'd then backtrack and try to figure out if this is actually Nazi or if it is the other connotation, but I'm not a Jew. I haven't been attacked for my genetics, nor do I have being starved, forced into labor, gassed, experimented on, nor vast discrimination in my recent family history. Keep in mind, please, that some people still have grandparents and great-grandparents that lived through that. They grew up with stories of the horror that faced their people. That very symbol provokes anxiety of a time which still echos today.
So, whether you think it's right or not that they're offended, please at least try to see their perspective. That's the only way you'll be able to have a productive conversation because I'm willing to bet the majority of them are sick of having their feelings dismissed. I don't care whether you think it's valid reasoning or not. You cannot ever change someone's beliefs when it comes to something like this without understanding why they believe what they do in the first place.