"and it's not really sporting to accuse Shopenhauser[sic] of "narrowness of view" in regards to "overcrowding" and "social evolution" - he lived from 1788 to 1860, and, perforce, his views are dated accordingly"

I agree. It would be interesting to see what the pundits of 2206 will have to say about our philosophies and pronouncements.

IMHO politeness and manners, ie what society decides are acceptable behaviours and styles of speech, have existed in many non-island and undercrowded societies. They do become much more important when a society is under stress such as crowding.

My take on "combining politeness and pride" especially given the era in which it was written is that politeness e.g. kneeling and an outward show of inferiority before a ruler could be difficult to combine with the knowledge that they are in fact inferior in ability, intelligence or even monetary worth.
Although it would get easier when you remember that they could have your head cut off.