less wrong has a lot of opinions of the form "X is obvious and if you don't believe X you are crazy"

This strikes me as a problem of presentation more than anything else. I've had computer science professors whose lecture style contained a lot of "X is obvious and if you don't believe X you are crazy" -- which was extremely jarring at first, as I came into a CS graduate program from a non-CS background, and didn't have a lot of the formal/academic background that my classmates did. Once I brought myself up to speed, I had the methods I needed to evaluate the obviousness and validity of various Xs, but until then, I sure didn't open my mouth in class a lot.

In the classes I TAed, I strove for a lecture style of "X is the case and if you don't understand why then it's my job to help you connect the dots." That was for 101-level classes, which LW is, at least to my impression, not; if the Sequences are the curriculum for undergraduate rationality, LW is kind of like the grad student lounge. But not, like, a snooty exclusive one, anyone's welcome to hang out and contribute. Still, the focus is on contribute, so that's at least perceived social pressure to perform up to a certain standard -- for me it's experientially very similar to the grad school experience I described.

We're talking about opinions here rather than theorems, and there's a distinction I want to draw between opinions that are speculations about something and opinions that are ... personal? ... but I'm having trouble articulating it; I will try again later, but wanted to point out that this experience you describe generalizes beyond LW.