It has a long history in Western culture. Antisemitism is the worst sort of xenophobic nonsense and it brings out the worst in people. It has no basis in fact.
Pre-Revolutionary America was a better place for Jews than Europe -- and even here, they were not allowed to participate in elections (community councils and the like) until the founding of the United States.
The Pittsburgh killer explicitly stated antisemitism was his motive. This is entirely unAmerican, counter to the freedoms protected by the Bill of Rights, and should be repugnant to all decent people.
There's a gun show in town this weekend and I was thinking about going. I still might -- but there are a couple of vendors who show up from time to time* that I would have a very difficult time not calling out. They always have significantly fewer browsers than the other tables -- unfortunately, it's still a non-zero number.
This pernicious notion is the precise opposite to the American ideal of tolerance and freedom. It should be opposed vigorously whenever it shows up.
If you're thinking about making a "Yes, but..." comment or worse to this post, do us both a favor and ban yourself now. I won't have it. I'm not obliged to tolerate poison and I won't.
* Neither of them sell guns; each specializes in an only slightly firearm-related thing, different to the other. At least the guy selling bath towels and coffee mugs with pictures of Nazi leaders on them stopped showing up.
4 months ago