You're absolutely right. Silence was seen as being courteous, but when it's a rage-filled ominous silence, the quiet before the storm, it goes from polite to nerve-wracking. And I believe in a lot of cases, it might turn implosive rather than explosive, leading to depression, and self-numbing behaviors on order to silence the anger that can't be expressed.
I also agree with you that the flip side is learn when to use it. There's a world of difference between people who use others as one gigantic ear to dump their shit into at completely inappropriate times, and people in relationships struggling to improve but without the tools to do so. In the first scenario, silence would in fact be golden. In the second, the gold has turned to dross.
It also makes me wonder if gender plays into it. Assertive communication may have been more encouraged (or tolerated?) for males in my generation than for females.
Interesting thoughts for me. Thank you, Marcus.