Not your problem how other players manage.
Smugnorant players tend to ignore good advice and then wonder why they can’t clear the upper dungeons and raids.
Play your style, get a good guild and don’t worry about it. You want a guild of veteran wow players, not a bunch of retail noobs who think they know everything.
Sounds really bad. My condolences.
They must have used spell reflect. 
Stop acting like this is a PUG problem. Guild runs of dungeons and pugs are no different. They are the same people. Being in your guild doesn’t make them better players. Nothing about this commonly spoken nonsense is true whatsoever.
Your responsibility is to keep aggro off of the healer. If dps pulls aggro on a mob which I’m not attacking it’s their responsibility to lose it/handle it. I’m not going to run around like a headless chicken chasing the mob you pulled aggro on if you’re dps, distracts me from watching healer and looking around for adds. Has always been my policy and nobody seems to have an issue with it. Tbh idc as long as the dps doesn’t wipe us with their decision making. If the healer has an issue with healing dps and tank then the dps can be told to tone it down a bit, otherwise idc.
Maybe you should stop trying to tell other people how to play. If they want your ‘advise’ they will ask for it.
Welcome to tanking. 
You gotta let em fail. If they don’t like you telling them how you tank, they don’t get to tell you jack if they pull agro and eat dirt.
I personally had no idea about vanilla tanking until I went to the forums. My first tank experience was in WOTLK as a tauren paladin. I had absolutely no problem with people attacking before I got there. It was a trifling matter to get aggro.
Now I come back to vanilla no longer a WoW noob to find myself a classic noob because I only played for 3 months before TBC and none of that was competent. I imagine my story is the same for a lot of people, not necessarily the tanking bit, and knowing people you’re bound to get a decent chunk who’ll behave negatively to learning about these mechanics as they existed in vanilla.
I can for sure seeing him kicked. I can also foresee most groups rolling with it though.
As others have hinted or said, this entire story is a case study in why LFG people wait 30-60 minutes to find a tank.
Tanking in Classic IS slower and more difficult. People would rather complain about others than recognize that gameplay adjustments are needed.
You rolled a low charisma score if you cannot explain this information to people successfully.
It’s good info but you’re just bad at explaining it.
If it’s one or two instances, you’re probably playing with a-holes and are better off without them.
If it’s consistent, you’re probably the a-hole and need to change your positioning.
Try putting on a 2hander and opening with sweeping strikes and whirlwind and then use a hotkey to switch to sword and board and then start sundering. That will generate a lot more threat to start.
Was your advice in response to actual wipes or given in principle?
my advice is, start your own group, and get a healer who’s on your side. After so many deaths, the DPS will listen to you
Bad at explaining has no way of being on the same line of just insulting people.
Anyway to the OP. The thing is just roll with a dungeon. In lower levels you don’t even need to tank at all. If there are constant wipes and people have an issue with this they will voice it. Thank god they voice it that way you know who has absolutely no idea how the game works to blacklist them.
Don’t argue with them. Just report them and move on. You might actually be clumped into the GM’s penalization if you’re escalating the situation.
Maybe you need to rethink your educational methods if you are trying to explain something. Some people think they’re “explaining” stuff to others, but in reality they’re just being egotistical studs.
I used to talk about the tanking mechanics and ask people if I could pull first and all that such 15 years ago. What did it do instead? They labelled me as an a*shole with the attitude of “don’t tell me what to do.”
I’d say whether you’re wiping or not just don’t say anything all the way to the end. If they insult you or so just report them and move on.
But if you really need to voice your opinion do it when you’re playing another role. Like if you’re DPS or healer than talk about the tanking mechanics. For some reason people respect the healer and will listen to you. As the healer tell others to let the tank get the aggro. Because they don’t want to piss of both the essential backbones of the group (healer/tank)
It’s a community attitude adjustment.
i bet you were anything but calm