I understand what you are saying, and as much as I try to convey the nuances of medicine to patients and explain risk/benefit analysis, the reality is I get into way more trouble with this approach than the docs who just say, "this is how it is," with utter confidence and absent hedge.
Patients want you to be sure. They don't want choices, they want answers. And if you can't tell them with confidence things that you can't possibly know, they'll find someone else who will. I'm OK with that. Most docs aren't and are more than willing to play the part of the over confident narcissist. It's what patients want, after all. Until people stop rewarding narcissistic behavior with their praise and worship, instead of recognizing it for the personality disorder that it is, the world will continue to be ruled by these horrible people.
The implication is that you're jealous or bitter or self-insecure and you feel the need to divert attention away from yourself by hating on something you actually like or would otherwise treat with indifference. I think lately it's uses also include a placeholder phrase where people readily accept your opinion, but are otherwise unsure as to how to respond but by saying something essentially meaningless as this. In this second use, it means simply "I acknowledge that this is your opinion and have nothing to add". Finally, when uttered ironically (smug grin optional), it can mean the same as the second use, but also add a hint of goading you into going on a rant. In effect, the speaker knows of the first use of the phrase and relies on the hearer to also know of it, so the phrase is uttered to provoke either a reaction or merely a continuation or reiteration of the strong opinion.
I always read it as reserved agreement tempered with shock that someone would actually speak their mind plainly. Apparently, stating your opinion frankly is just not something that polite people do. You're supposed to format it for general consumption...like using a feedback sandwich. Maybe a vegetarian feedback sandwich (without the meat).