Rabbi Small and the Absence of Guns

When I read crime fiction, I'm usually not reading it for the puzzle of who-dun-it, but for the background details of different ways of life. That's why I like the Harry Kemelman series about Rabbi Small. He's the rabbi of a Conservative Jewish temple in a small town somewhere near Boston in the 1960s and 70s, and the books go into some detail about the inner workings of the temple and the Jewish religion. With added murders, which Rabbi Small solves by applying rabbinical scholarship to the problems.
I've just finished reading Thursday the Rabbi Walked Out (all the titles include days of the week), which brings Rabbi Small to his twelfth year as rabbi of the congregation of Barnard's Crossing, and somewhere in the early 1970s. Women's lib and sexism form part of the plot - women in the congregation want to take a full part in the synagogue services, while at the murder scene the police think a woman must have done the shooting because of the erratic nature of the shots fired.
And that's where I started pondering. It's not long ago that there was a massacre at the school in the town of Sandy Hook - a town that I imagine to be similar to Barnard's Crossing. I remember it being described by residents as a nice place to live, friendly, with a low crime rate - and yet the first woman to be killed (by her son) thought it necessary to keep assault rifles in her home.
Back in the 1970s, the murder weapon is brought from the local bank to the scene of the crime by one of the tellers - the guns were bought to make the tellers feel safer because the bank did not employ an armed guard. The old chap who lives in the semi-derelict old house on the hill does not have any weapons in his house. Nor does the ex-Captain of Marines who is president of the temple, it seems, or any of the other characters. Only one character is described as being keen on shooting - he spends a lot of time at the pistol range at the local yacht club - but he deliberately doesn't have a gun licence so that he isn't tempted to use his skill with a pistol to solve his arguments for him. Oh, and the janitor at the temple goes deer hunting occasionally - but that's it.
So how did small town America get from there to a situation where an ordinary woman thinks she needs an assault rifle?