I know it's hopeless, but since you ask: it's topicality. Usenet is a
huge space in which people can discuss anything they want (even if most
of it is now a ghost town). If you want to have a conversation about X,
you go to newsgroup X. For topic Y, you go to Y.
So, when people go to comp.lang.c, they want discussions about the C
programming language. When they go to comp.arch, it's because they want
to talk about computer architecture.
If I go to comp.lang.c and find somebody bringing up some totally
irrelevant topic out of the blue, it's an annoyance. It doesn't matter
if it's dog training, guns, 3D printing, or model rockets, it's still an
annoyance (why did I pick those topics? Because they're all interests
of mine. Just not interests I'm expecting to hear about here).
The more someone persistently, incessantly, continually, insists on
bringing up an irrelevant topic, the more frustrating it becomes, and
the greater the extent they get ignored.
So, yes. The reaction to your posts ranges from embarrassment from
those of us who actually agree with your philosophy but would prefer to
set an example that might encourage someone to follow it rather than
make people actively hostile, to rage on the part of people who disagree
and don't want to hear about how they're wrong.