The article includes comments from the episode's writer Larry Charles suggesting that the episode probably came too early in the show's run (only their ninth), and so no one was quite settled with what later becomes the program's standard. The director of the episode, Tom Cherones, was outspoken at the time -- and quoted extensively today -- that the episode was wrong, and that "You can't make a funny show about guns, in my opinion."
I don't agree with that statement, nor does Larry Charles, though from what they write about this specific episode, it does seem like they have things in it that are pretty uncomfortable, and it probably was right to pull.
As a side note, the article also contained a sequence about what Kramer's first name was. And it was different from what we later learned. But because the episode was dropped, so was the idea of naming Kramer, and they didn't deal with it until years later.
(Note: in the first draft of this, I referenced Larry David for all the "Larry's." I've since corrected the appropriate attribution, and noted Larry Charles properly. Sorry.)