It's a bit like Tony Blair not grasping the difference between begging and mugging. One might behave in any number of ways, but the possibility doesn't make the act of tapping on the window intimidating in itself. That motorists sometimes react as if the act of tapping on a window is some kind of shocking intrusion, impertinence or threat is their problem.
I paste, below, the passage (entry #78) that seems to have been the cause this recent discussion on window tapping:
As a comment: It can be quite intimidating to have a road user approach you in traffic and tap on a window. It hasn't happened to me, but women I know have been quite freaked out by it. That may sound silly, but in the first two seconds you have no clue as to the motive of the 'tapper'.
Before now I've flashed people who had a flat rear (hard to detect from inside some cars) and they gave me the finger when they saw me pointing at their wheel. I do sometimes think that are initial responses (motorist and cyclist) are now set far more on 'defence' mode than 'dialogue' mode.
Personally, I'd have no problem with someone tapping on my car window - but I can see how some might take it as somehow intrusive or threatening."
I'm not sure anyone currently in this discussion is suggesting that the act of tapping on a window is intimidating in itself. I certainly didn't say that.
What is being said here (as quoted above) is that some road users might take it as somehow intrusive or threatening.
That is not 'their problem' as you suggest it is.
I've been to weddings in Montenegro where the male party surround the bride's father's house and fire into the air until he emerges with his daughter (the bride). It's spectacular, it's traditional and it's expected. It is somehow magnificent to behold. I've even been mocked for showing up at a wedding without a weapon. Once the bride has emerged, magazines are emptied in celebration. It is very noisy.
However, had anyone happy-fired into the air in celebration at my wedding in London, I might have felt slightly threatened. A person's reponse in these situations is not a function of the intent of the happy-shooter or the window-tapper. Both could be perfectly benign and usually are.
The issue is that some road users find the action of tapping on their window disquieting. I don't. Some do. It's just worth bearing in mind.
It's not 'their problem' and it doesn't mean they probably shouldn't be driving.