However, if the conversation began with my friend telling me "you will probably just dismiss this" and especially "many others believe this" I would feel insulted/dismissed.
When talking about lies people tell each other, the beliefs are the topic, whether or not you believe they are lies or truths. If you don't want to have other people weigh your beliefs in such a context, I would suggest not mentioning them during such a discussion. There are beliefs I have which I'm sure most don't share, but which I don't feel the need to defend (anymore) at every opportunity. For example, as an atheist, I wouldn't typically go to a Christian forum and announce that God doesn't exist, unless I were prepared to have my views ridiculed.
Please don't take this as meaning I think you shouldn't discuss your beliefs in this thread, but only that I think you shouldn't try to influence others not to debate you honestly by implying they're being uncivil.
But, no one has beliefs independent from any kind of cause or reason. So, just because someone says you should respect what they think because they believe it does not mean you should reject their belief due to bad justification.
Belief qua belief does not deserve respect. That is a self-serving myth told by believing people.