It's not really that saturated or mono-unsaturated fats are good for you, but that poly-unsaturated fats are bad for you. I realize this is contrary to what much of modern nutrition says, but the lipid science says the poly-unsaturated fats are worse because they react more with other molecules in your body.
Also, saturated fat consumption has been declining and unsaturated fat consumption increasing over the past decades while health keeps getting worse. To me, this suggests that something is wrong with our current nutritional understanding, and I believe the lipid science shows that the problem is the poly-unsaturated fats (as one part of it at least, it's obviously not monocausal).
Why is Canola oil bad if it has the same quantity of monounsaturated fats as Olive Oil?