I think that ‘proper etiquette’ assertion is likely not universally endorsed. I had someone posting threads ridiculing what I post, and me, on a daily basis and every time, he followed ‘etiquette’ and pinged me. I asked him to stop. I don’t want to be spammed by people like that and I am not ready to assume others want me posting to them.
It’s a longstanding FR rule (and nettiquette) for the simple reason it isn’t cool to talk about people behind their backs. It’s just basic human decency.
It’s also an old FR rule that if someone asks you to stop pinging him or her, you stop. In the example you gave, the other Freeper followed both rules.
If you choose to make up your own rules ...
Not to mention all of the posts that bash you, without pinging you.
So, the hypocrite whiners can whine away.