If what you say is true, then that weakens the authors thesis pretty drastically.
For example, you say: "even the Jews didn't believe it until the news broke out in the final year of the war in Europe". This uprising took place almost two years before V-E day, which means the Jews in Warsaw were not aware that they were "literally" fighting for their lives. They were instead fighting for their human rights, and their way of life. (We know they were destined for extermination camps, but they didn't; if what you say is correct.)
The author also points out that the deportations were 'ostensibly for resettlement in labor camps, but almost always for extermination' and 'Often, the Judenrat was told that as long as the ghetto worked hard to produce factory goods for the Germans, the ghetto would be allowed to survive.' Thus, how did the Jews of Warsaw know that genocide was planned for them, and not, say, work camps?
If they did not know, then thesis - that weak gun laws can help prevent genocide - is actually a broader one; that weak gun laws can help prevent ghettoization, or that weak gun laws can help prevent mass deportations.
Hence if there is any lesson to be learned, it sounds like the author is arguing for the increased weaponization of the Palestinians, in order to better reach the long agreed upon two state solution.
Another issue is that you added your own qualifier; "Tribal genocide ... cannot be just as easily compared to the Holocaust."
This is a different definition of genocide than the author. Or rather, when the "International Society for the Prevention of Crime", concluded "defensive measures are the most effective means for the prevention of genocide"; did that mean genocide as defined by the Genocide Convention? I think so. While you want to exclude "tribal genocide" from that definition.
In science there is an analysis error called "p-hacking". More specifically, if the correlation across the entire data set is too weak, some people will look at a subset which has a more detectable correlation. (XKCD calls this 'Hey, look at this interesting subgroup analysis'.) The problem is, the method of subsetting should be part of the significance analysis, and by excluding it, the p-value is artificially raised.
By choosing a subset of 'genocide', you weaken the intent of the essay. You say they cannot easily be applied to tribal genocide, which opens up the possibility that the can't be used for other genocides, and especially opens up the possibility that it can't be used in the US political context.