Yeah, to address folks above.......I did mention "gross negligence" for a person in front of you. So ymmv depending on that.
An example of a person in front of you in greenway trail would be an off-leash dog person where the trail curves and doesn't have visibility. If you hit the dog, their fault. Gross negligence. If you were going 25mph on a greenway, you start to share some negligence as you were both breaking the rules.
This is why these groups need to be somewhat disciplined. Even USAC has the centerline rule and I've seen the moto go up and chat and threaten to pull riders.
My thing with the "weeknight worlds" stuff is that there is no medal on the line. No podium. I work for a living and need to get back to the family and work. So if you wanna do stupid ****, I'm likely to ask the vets in the group to sit up and let the "stupid" think they've won the ride by breaking away. Then once they're gone, continue on.
I think some of them just get way way too big or the routes are featureless enough that some Cat 6 folks can suck wheel forever. I know, just don't go if you don't like it. Sure. But I just feel it doesn't foster good community among other riders and cars if the blob is too unruly. Our weeknight worlds usually starts with 20 and about 4 to 6 start a hard rotation on front. Folks will fall off the back, jump in rotation, attack, etc... Nobody really goes over the yellow. We get tight if one of our Garmin Varias shows a car back and we wave them on.