One thing which I think causes people who are in general terms "on the same side" to talk past each other in politics is the failure to understand that people just have different priorities from each other. "We" might all agree on 10 issues that are important, but we don't rank them all the same away. I don't really expect that everyone thinks that SUPERTRAINS are the most important policy issue (not that I do either), but I might have some good reasons for thinking they are nonetheless.
Also, too, some people just like to be assholes on the internet. We all need a hobby.