I'm not a group rider, but I'd be inclined to side with the group leaders' decision to ask you to not ride with them. There are certain etiquettes for any group activity be it a ride or run. Showing up without a helmet is seen as a disregard for your personal safety so why would anyone in the group feel you would respect their safety? If it is an organized club or group, the waiver is not an unreasonable request as well.
I have profound hearing loss, I'm an introvert and anxiety that would make me worry about being "that guy" that spoils another's enjoyment have made me avoid group rides. However if I did join one, I know that I would need to abide by the rules of the group be they club structured or simply a friendly group activity. I think you should look into why the group did not welcome you and correct those things before joining another group ride.
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"It is the unknown around the corner that turns my wheels." -- Heinz Stücke
Last edited by Chuck M; 06-23-21 at 05:40 AM.