what you're missing here is a class analysis. that is, we still don't know why these words are "bad".

you'll notice that the crude words are all very german sounding, and that they start to develop a crude context around the time of the norman takeover. english is of course a german language (spoken by invading angles and saxons). the norman ruling class mostly spoke french.

so, you ended up with certain words being looked down upon because they were only used by the non-aristocratic classes. to use these words would define you that way. avoiding them was consequently of the utmost importance, to maximize social advancement.

we don't swear like dukes, or duchesses. we swear like sailors.