So there is upstream spam filtering. Thiss seems to contradict what you said: "There is no administrative ostracism. Nobody gets kicked out by brownshirts for expressing their view."
Spam is an expression of views.
Spam is an expression of views.
If you think that spam is a form of expression, and you're interested in it, all you have to do is post a few articles and use your real e-mail address in your From: header.
Then no overbearing NNTP server admin will stand between you and your spammer friends.