John, as I posted earlier, I do have sympathy with your position on this - but I think it should be a free choice. The site owner already has the ability to close down an account if they wish.
In my amateur photographic life I have been a member of a local camera club for around 15 years, and we meet once a week. It is customary for a fair size group of us to go round to a local pub at the end of the evening - the group varying from 5 - 15 or so. We pull a few tables together and all sit around and chat (and have a beer). Sometimes the discussions break down into smaller groups, and sometimes the whole table is sharing one discussion. There are often quite conflicting views. The subjects are varied, but many of them are about photography - mostly aesthetics rather than technical. The characters present are very varied too - a good cross-section of local people.
When I participate in posting on this Forum, I almost imagine myself sitting around that table in a pub with a group of varied folk, discussing the issues. I would never behave in a manner, or say anything that I wouldn't say across that table face to face. Thus to sit and speak from behind a screen, anonymously, is not acceptable to me. That is my personal benchmark. Everyone has to make their own decision. I can understand there may be some rare cases where a person may need to keep their identity private, and I can accept that. But if they do, I believe their online manners should be impeccable. As Chris has just said, pseudonyms have a shorter leash.
As to the poster who worries about showing up in Google searches, don't say anything you don't really believe to be right. And anyway, I did a search of my own name and despite having made hundreds of posts here, not a single one showed up in Google. Only pages from my own website, and those of a writer with the same name.
So, like most areas of life, it should be down to personal choice and principles. Are you an upfront kind of person who speaks their mind face to face, or would you rather hide from sight and comment from the shadows. If the latter, just remember that we will be less tolerant of bad behaviour, and perhaps suspect your motives.