I doubt that he's the only person who has decades of years of experience in MMO. Infact I think I'm one the "youngest" when it comes to mmo experience (I'm only 27, but I've played dozens of mmos already: many others are probably twice as old). Sure he probably knows what it means, but I ask again this: how does he know that parser will ruin the game? As far as I'm concerned I don't see much toxicity due to parsers, I see toxicity due to OTHER things. I'm sure he knows (or at least has some information about it), but my point is that there's no absolute truth that parsers will ruin the community and in my case, I don't see many parser users blaming poor dps for their performance. So again, we have no solid proof.
The game has only one rule: having the highest dps possible while doing mechanics flawlessly without dying. Anything else is irrelevant, but that little that there is has to be done perfectly or else you're not doing any good. My opinion here is that it's the game's fault that everything is based around pure damage, while mechanics are just a nuisance more than an actual tactics. In most mmorpgs I played tactics were made to so that some bosses were different than others and while there were dps checks, they were usually tame and rare. Plus, if you miss any mechanic you usually (USUALLY, as in not always) make it wipe. So people complain a lot because the game demands high skills in later content, which is the base of the game. I don't raid anymore but Coil required alot of work, work that didn't feel really satisfactory and that personally didn't click with me.
They already exist and, in addition, you're free to report them for harassing and shaming. I have one but I never harass anyone, even if they're terrible: everyone has to start somewhere afterall, but there are people who will harass them and they existed long ago. And parser users aren't the only players who harass others.
You are right on the fact that it's not allowed and that it's not forced, however I can assure you that not everyone will use it to boost their ego. Proof? Me: I only use to help improving my dps and that's it and, as I mentioned several times, it was thanks to the parser that I found out that I was actually better than I imagined. Sure, some players are like you say, but not every parser user is that horrible and I actually met them. Don't generalize everyone into one category: not everyone plays the same.
For starters, SSS dps isn't the same as in the real fight because 1) Your stats will be increased due to group bonus 2) Just like you said, movement. Let's assume I have 1500 dps: I can assure you that my dps won't be as high during the real fight, because there are a lot more scenarios where I have to survive a mechanic or two. And yes that's common sense. However you still have no idea how you'll perform in the real match: you might be the worst dps of the group without realizing it, and because you're trying to memorize movement, mechanics, rotations, cds, and so on. SSS only provides you with one information: "You have achieved the dps threshold for X boss", but it doesn't tell you "how much" you will do or how much you have done to it.
And in a game where all raid bosses are essentially dps checks, this is a very important detail to have, but I only speak as an retired raider.
I don't have issues accepting advices and I don't really get that defensive (unless angered). Infact someone already countered me saying how my BLM isn't that great due to the lack of SS, and I replied simply by saying "I agree, but I don't really feel the need to". However I see that you're only speaking about the worst of the people without realizing that there are people who will be able to teach things: I did that several times quite a while ago, and without being nasty or anything. But you just imply that we're all bad and terrible and that we're all going to slap them for their bad performance. Again, stop generalizing: there are people and people.
I agree: as long as people do their contribution, I have no issues with their low dps (not that I ever had to begin with). I don't have to get over myself: we're a group attempting to do a dungeon/raid, all I care is finishing said dungeon/raid, and doing it at the best of our skills. Everything else, at least for me, is irrelevant, parser included, since we defeated the boss. However I still wish to know how I fared, and so I test myself. And I'm sure others do the same. And I'm sure others only want to anger and harass. Both scenarios can happen.
If someone asks me advices, I tell them. If they don't ask me, I don't. I think this is a pretty straightforward discussion, but you're constantly making strawman discussion all through the post. I can assure you that I do not react that way and despite my "carelessness" I do care about the completion of the dungeon, and having everyone knowing what to do is more helpful than having people dying for not knowing tactics. Unfortunately not every group likes to wait and getting explained: I had a lot of mentor runs where I ended up in Ex primals but I was unable to explain due to some random puller. And it wasn't just one who did that.
But again, you just seem to be using various false accusations and generalizing every parser user as "bad people", while I can guarantee that not ALL of them are bad. I definitely don't consider myself bad, even though people have told me that I am, but as long as I don't cause issues (which I never did), and don't harass people (Which I don't), and use the parser for my own benefits (which I always do, unless asked), I simply do my own stuff. But THERE ARE people who harass just for the sake of harassing. And that's 100% fact.