1) There isn't so long as tobacco and alcohol are legal, along with a ton of other drugs that each have (potentially dangerous) side effects.
2) Is irrelevant to 1) and as you say is silly, but posters in this thread have already provided instances where cannabis users themselves have said it provided insight. Proving whether or not cannabis is responsible for that is impossible, but I don't see a reason to refute their personal experience unless you are heavily biased against cannabis in the first place.
This thread also has numerous instances of the italicized statement.
I mean sure, it can provide insight, it also can make you sit in a chair and re-read the same page in a book 10 times until you finally understand it... it really depends.
These are two totally separate questions.