Place these links on the page for links so everyone will see them.
I agree, the make-up of the group is extremely important. I run two class in Portland OR and the whole key is to set some guidelines and build camaraderie. My groups contain both male and females. We have been known to attend funerals for a fellow writer, even. Right now we are sending cards and reaching out to two members with cancer. This is how close a class can be if the instructor leads it with compassion. Some groups may not have a leader/facilitator. Maybe that would help.
Maybe there only needs to be a recognition that each person has their own voice and that is equal to all others to prevent intimidation. We take time to comment on what we like from each story, ask the person to tell more if they need to do so. We only offer writing help if it is requested unless there is definitely something blatant. This criteria needs to be established from the beginning.
Hope this helps,