There's an awful lot of "it depends" to all of these scenarios. It may even be possible that there is, in fact, some scenario where I'd be OK with what's quoted above. But generally speaking, I would not be happy with something that comes off as smug and suggesting a "I'm the teacher, and you're the student, now let me show you how stupid you are" mind-set. But if the person speaking had the right standing in my world-view and I was really stuck, well then maybe I would tolerate that (even if it wouldn't be my preference).

I lean towards the kind of language I mentioned in another comment, with things like "Hmm... have you tried _______?" or "The first thing that occurs to me when I see ______ is ________" and so on. Or even "Do you think that maybe _________?"