Hey Snaf', I know you're probably tired of getting replies to this and don't worry, I'm not offended as I say this-- but you have to remember that a good portion of the people who complain about withdrawals are experiencing the very symptoms/issues that they were medicating away with weed, whether knowingly or unknowingly.
Say somebody has depression, just to pick an easy one. Weed makes them feel better... in some cases it's a cure-all. Then they stop smoking weed and, just like with a benzo' addiction, they suddenly experience that rubber band snap-back effect where all their ailments that they had under control rebound to new heights, and it can be overwhelming. A lot of it is the user's ignorance of their own individual psyche and physiology and then suddenly having to cope with their lives without weed.
That said, I agree with you that weed withdrawals are almost all in your mind. Almost. I know what I've gone through and I can't label a loss of appetite, tremors out of control, sweating out of control, as "in my head." It's clear that my body's physically acting differently when I abstain for ~36hrs. I guess the money shot here would be somebody proving that those physical symptoms are a result of an anxiety/stress spike upon cessation of habits, but it never felt that way to me. I also agree that benzo' and opiate addiction are both physical hells, no way around that. It's way worse than breaking a weed habit, but at the same time... it always seemed irresponsible to me to shrug off a person's cry for help with something that I have experience with. Turning it into a dick-measuring constest is never constructive, never helpful.... it just comes off as a way of telling everybody how big your dick is.