Is there a problem with a slower ride just letting a faster rider "go"? We've had fully-enclosed velomobiles show up to group road rides. When they decide to put the hammer down and start pulling away, nobody chases, or even really cares.
I've been guilty of burying group rides, but it's usually after somebody else brings the funk and the noise. I've successfully countered attacks, only to be told "this isn't that type of ride" after I end up stopping and waiting, which is super confusing.
I explained "guttering" to a newer (but seriously strong) road rider during a group ride last year. He tried it out when the group was strung out and ramping the pace towards a known sprint/regroup spot. He then got berated for guttering and told the usual "this isn't that type of ride."
It seems like a lot of group rides can only be as fast as the most fragile ego will allow.