I love your posts because they are thought provoking--this one in particular.
I think there is a difference between being yourself and provoking a fight. Is the meetup a networking mixer or is there a theme for it? The purpose of the group might dictate the tone one would take at that meetup. If the purpose is to make business contacts, you might not necessarily want to talk about things that would cause friction and thus defeat the purpose of the group or or your being there.
You know the old phrase about how politics and religion can very easy polarize people. I think its because these subjects are so complicated that people can take an opposing stance and both people can be right in some way and still wrong in others. Socialism and capitalism are both good in some instances and bad in others, I think. How which system effects you personally or people overall depends on the person and what parts of that system we are talking about. The Sanders campaign sounds wonderful for you. whether socialism could work in such a large, diverse country as the US with a history such as ours is a big question.These are very sweeping subjects and topics within them usually involve tons of history. They are also very emotional subjects, especially religion, because one must make a leap of faith for belief and they involve concepts that we are very passionate about.
I myself wish that things were so black and white that one system or one religion had all the answers. How simple that would be! One of the reasons I am proud to be an American is that we TRY to be tolerant of various ideas and various cultures. No, sadly, that is not always true as you have discovered.
Being yourself might mean talking about your interests or hobbies, what you do, your ambitions, etc.
Regarding someone calling you a loser because you havent dated etc, that seems so bizarre and unusual to me. Usually people have some reason to expend the energy to be hostile. You have described the San Francisco dating scene as being abrupt and cold. Maybe its that. As if these people are so rushed to find the dream date that they cant even be civil. Phew. To me, many people are potential friends, not just potential dates or life partners. Hey, lets go for a coffee, etc.I dont get that kind of attitude at all. However, life in some really big cities is definitely "life in the fast lane". Glad you are planning to move.
I just realized that one thing a man might not be thinking about is that, tho science has extended this window, women have a biological clock in that their childbearing years are limited. Food for thought, I hope.
well, hope this helps a little.