[gjm11]

If I write "I think Google is evil", I mean: "I think Google is evil, but I acknowledge that it's possible for other fairly reasonable people to have a different opinion."

If I write "Google is evil", I mean: "I think Google is evil, and I consider this an established fact that reasonable people shouldn't be disputing."

These are different propositions, and I might want to say either of them.

A policy of not using qualifiers like "I think" because of-course-it's-my-opinion makes it harder to make that distinction. I don't think the advantage of punchier prose is worth that loss.

(Note the "I don't think" at the end; other people might reasonably see the tradeoffs differently. Note the absence of "I think" elsewhere; I don't see much doubt that there is such a tradeoff being made.)

[moron4hire]

A reasonable lesson should already think it's possible for other reasonable people to hold different opinions, and not feel threatened by them. It's only in this bullshit really of the internet that we decided to start interpreting the things other people say as "potential facts in need of disputing" rather than just "the utterances of peers". The former mode implies a level of deference that we don't take on in public, face-to-face conversations.