When I run into people like this, sometimes I like to ask them "why is this issue personally important to you" or "how did you get interested in this issue" - because that gives them space to talk about it and you get a sense of what their emotional connection to the issue is. Then depending on how strong that connection to the issue is you might be able to sway them with some facts or your personal reasons for why you feel differently. Maybe you did that, I don't know. But in general a lot of people keep things at the intellectual argument level and at that level people almost never change their minds and just get angry at each other. Sometimes if you find out someone's emotional connection to an issue you can even be around people whom you really disagree with because both people have understood the other's motivation.