My full thoughts on the matter, and why I'm sad despite expecting Dan and Jason to be fun additions, can be read in the link (warning: >1001 Words). Regarding the latter part of the post title, the following is a slightly modified forum post but I wanted to keep it around for future use:

The "lack of politeness" stems from being ignored or harassed every single time they voice their concerns, no matter how considerate and civil their tone. This pressure has built up over a long period of time, the better part of a decade or more in some cases, and the past few weeks in particular have seen a lot of exchanges about these issues.

Is being infinitely patient with even the worst people the best strategy for winning the most people over in the shortest amount of time? Probably. But that's not a realistic or fair expectation to hold anyone to when they're the target of personal attacks and threats. After a short time participating in these conversations, it becomes apparent that a disturbingly large percentage of people replying to you are more interested in anonymously throwing abuse your way (often with rather obvious dummy accounts) than honestly engaging you and trying to learn about your perspective. When my hands start shaking and my teeth start chattering, it gets hard to keep an even keel when I suspect the words I'm writing or saying are directed at a brick wall.

I'm too depressed and anxious to devote much time to this kind of conversation, but in the very limited time I started wading into these waters I've been met with an astonishing amount of vitriol simply for expressing my disappointment as non-confrontationally as possible. The productive conversations I have had with people who genuinely wanted to learn from my perspective have been heartwarming if not altogether satisfying in every way, but this stuff is incredibly draining even after just exposing myself to the storm for a few days. But sometimes it becomes clear when someone's bullshitting you. Lashing out in that instance is a form of immediate catharsis that I don't begrudge anyone when they're dealing with all of the nonsense I've seen and tons more.