Get off it HeadyNuggets, your post smacks of this defiant will to prove something. This is Bluelight, not your disapproving parents or friends. Marijuana can do many things, and some of them are, in fact, negative. Depending on how wrapped up you are in your own little world (which happens when you smoke up a lot), harm from toking can progress without you noticing it for a long time. These things are subtle, and subtlety is often overlooked.
Some people start to see chunks of their life being wasted through getting stoned. It happens to many people, some of whom those who have said what you say here.
Bottom line, don't object to the mere possibility of pot harming some people more than harder drugs have. It only shows how much you haven't seen.
To answer the question, yes, I've just gone and quit earlier this week and am astounded at how dulled my brain was from cannabinoids. But my answer isn't too important because I've only done LSD, DXM, and salvia besides pot, and only twice each.