Historian Joyce Lee Malcom has pointed out that a steady trend of declining interpersonal violence starting in the 13th Century reversed in a few decades. Others point out that "burglaries" in the U.K. much more frequently take place when dwellings are occupied than in the US. See the British Crime Survey, which as of 2009 said:
There were 284,427 burglaries.
20% of those were face to face.
In 59% of those cases, violence was threatened or used.
In 40% of those face to face encounters, violence was actually used against the householder, a rising number since such statistics were first collected in 2002-3.
If the subjects of the U.K. don't feel a need for guns for self-defense; maybe they aren't getting killed in large numbers, but they're getting brutalized, and that's very bad in a zillion ways.
The very definition of citizen, vs. subject or slave, is one who bears arms in defense of his polity.... (Although that's not something that Black Armband History mentions....)
Your "orders of magnitude" claim about school shootings is flatly WRT to Europe, especially Western Europe (which is significantly larger than the US in population), compare, for example, https://en.wikipedia.org/wiki/School_shooting#Europe and https://en.wikipedia.org/wiki/List_of_school_shootings_in_th... This is especially true about the ones of larger magnitude.
UK robbery incidences: 76,179 (THOSB – CEW page 61, paragraph 2.)
76,179 / 561 = 135.72
US robbery incidences: 354,396 (FBI – CUS)
354,396 / 3116 = 113.7
You are thus 1.1x (135.7 / 113.7) more likely to suffer robbery in the UK than in the US.
Now, robberies in the context of home invasions I don't know, and I didn't see it on that page. Nor did I see where you then got a 4x more likely to be killed if in a house invasion robbery in the US, although I'm quite willing to believe it. But I'll seriously look at that page, the author's inclusion of BCS and NCVS statistics means he's serious (as, e.g., a posting in the current "Dial 911 and get Wall Street" topic notes, US robbery statistics are understated by cities where they don't even bother with them if there's no injury).