I'd like to take a break from our regularly scheduled political rantings to focus on a linguistic ranting — but don't worry, it's one with political applications.
The story of this post goes back several years to a freshman writing seminar I took at college. At one point, our professor begged us to stop introducing statements that were obviously our personal opinions with "in my personal opinion." She pointed out that the intelligent and careful reader should be able to tell the difference between a fact and an opinion, and they should furthermore be able to deduce that since you're writing an opinion piece, uncredited opinions are yours.
I've tried to keep that advice in mind ever since. If you look back at my posts, you'll find (I hope) that I mostly present my opinions upfront. When I wrote that "a lottery isn't anywhere close to a governmental function," I trusted you to figure out that this was my personal opinion. When used the same tone to write that "68 HDBs times 419 calories per HDB is 28,492 calories," I trusted you to figure out that this was a statement of objective fact.
An explicit "IMO" is valid when expressing a factual statement without being sure of its truth: "I think Mary meant that Billy smells bad." But politicians and pundits (see! I told you this would tie into politics) frequently throw in "I think," "in my opinion" or even the dreaded "I believe" superfluously.
Why is this? I haven't formally studied it, but my theory is that it's a way of hedging opinions and anchoring them in an absolute, unarguable fact. Whether Jesus is the one son of God and rode dinosaurs is absolutely true or absolutely false (even if we can't absolutely determine which it is), but that I believe in a divine, dinoriding Jesus is indisputable, if I say so.
Americans are trained starting in preschool to believe in a hyper-egalitarian world in which everyone is entitled to their own opinion, and opinions are never right or wrong. There are limits to this; some opinions are clearly stupid. But since we're taught that all opinions are created equal — better yet, that they're all created valid — all we need to do in order to state obviously wrong facts is to wrap them in an opinion.
Can't find any evidence to support the statement, "the government will set up death panels to kill your grandma"? No problem: you can just say "I honestly believe that the government will set up death panels to kill your grandma" and deliver all emotional punch without any of the liability. I can't hound you about what you just said, because that's just like, your opinion, man.
Now, clearly [warning: opinion!], not every use of "I think" is nefarious. It's often what wikipedia tells me is called a discource marker: that is, meaningless filler (I'm sometimes guilty of this, myself). Sometimes it's even validly used to explicitly mark something as an opinion, if it could be misconstrued as fact. But it's often used to present facts without backing them up, even if that's done on a subconscious level.
We should expect our leaders and political commentators to have enough control over their language that they won't accidentally blur the lines between fact and opinion, and we should expect enough intellectual honesty on their parts to not do it intentionally.