When I tank I provide a service to the other 3 guys.. If they choose to not accept the service, it's not my fault.. I save my taunts for when the healer is in trouble, not for when a dps decides he wants to tank a mob himself..
Also, single silver mobs and below I don't care about tanking at all
The key to tanking with pugs is right here. If they're gonna try to make your job difficult, that's up to them, and I'll just keep doing my thing. If someone taunts off me for some reason they can keep it. If you pull ahead of me, I might try to round the mobs up but I'm not gonna stress out about keeping you alive.
I probably won't even say anything unless they cause a wipe (which they never have *flex*). But I do always put them on ignore. Don't like my service? Get the tank after me next time!