Here is an example of what I claim is not the case. We see angry arguments about all of those topics on HN. They're not even infrequent.

My claim is that you (I don't mean you personally, but all of us in your position) perceive HN as an 'echo chamber' on such issues precisely because it isn't. I imagine there are small biases on some of them, but people exaggerate this into "groupthink", "bubble", "echo chamber", etc., not because that's how it is but because that's how it feels.