I run meditation groups and if someone started trying to tell the group what to study, I would probably ask them to leave. I teach meditation is a very specific way. Not all forms of meditation are suitable or safe for 'westeners' - some are specifically designed for people who are in retreat from the world. I tell people that my philosophy is mine and that they are free to agree or disagree. Some people have left the group because they didn't agree and that's fine. They can start their own group if they have their own agenda to promote but I'm not going to engage in a debate or let them derail the class if everyone else is happy with the way things are going.
It's possible that the other members of the group thought you were interrupting and distracting rather than helpfully pointing out things they could study.
There's nothing to stop YOU doing more study on things you're intersted in or sceptical about, but it's not your job to point that out to other people unless you're specifically asked.
You have NO idea where people are at, what their level of knowledge or experience is or even if what you have to say is of interest to them. Is is not your responsibility to enlighten them.
A facilitated discussion group isn't a forum for you to start arguing with the faciitator or pointing out what you think is wrong or questionable. If you don't like it, leave the group or ask to talk to the facilitator at another time. Don't disrupt the group. I often get email or calls froms students with questions and things they don't understand - we discuss it and move on. We don't disrupt the whole class with an issue one person has if it's going to require more than a few minutes discussion. If most people have the same question or issue, then we discuss it in class.
Don't try and force the group to change. If you think it's doing damage to people, then sure, make a statement to that effect and give people your contact details if they want to follow up with you, but again, leave if it's not for you. Don't expect people to change to suit the way you want to study.
Many people attend such classes for companionship, down time, an opportunity to connect with like minded souls - not necessarily to have every topic subjected to academic rigour and debate. As for being a sceptic, I think that's a good thing - after 15 years of working in the healing/new age/spiritual industry I'm probably one of the biggest sceptics out there, but bringing it up in a class full of people who don't require the same kind of proof as you is not going to win you friends. Many people are open minded about things - they neither believe 100% nor disbelieve 100% and are quite happy to stay in that space and not dissect everything.
Having said tht though, I think the teacher was wrong to not speak to you in person and give you the opportunity to change the way you communicate. If you were in one of my groups, I'd tell you that I think it's great you're asking questions and I'd be happy to discuss it, but let's do it after the group as I have a particular curriculum to get through and that's what people have paid for, not to hear you and I debate things. If I wanted you to leave the group, I'd remind you of the above conversation and tell you it's really important that you above by this and if you can't, then I'd have to ask you to leave the group as it's detracting from the expereince everyone else is having. I might even help you to try to find a group that is more suited to your learning style.