I disagree entirely. Your argument for less material being less structurally sound is only valid when comparing exact materials. There are several different strains of graphite compounds (not sure if that is the right word) (I hate technical speak haha) that are used in rods and some of these strains offer a higher level of structural integrity than a rod made with a different strain using more material. To offer an example, my friend has a Ruger six shooter, I have a Colt. The Ruger is cast and has more metal on the gun. The Colt is forged and uses less metal. Both have similar structural integrity.
As far as your friends who broke their rods, that can't be used as validation for saying modern rods with thinner walls are inherently weaker, as we have to account for the human variable here in the situation they encountered, which can't be quantified. I'd like to know specific details on what caused the rods to break as in the diameter of the tippet they were using and how hard they were yanking on the rod. As for myself, I NEVER use a rod to break a snag. I sit the rod down and rip the line/leader out of said snag by hand. This avoids a rod break entirely. You can also lock your drag, point the tip of the rod at said snag, and pull to break it off. I would chalk the scenario of the rod breakages up to being user error but can't say for sure because I wasn't there.
Having owned a bunch of modern "thin walled" rods so to speak, I have never experienced any breakage. I stopped a kayak with one such rod, had the tip of another ripped off by another friend's fly line, and had said friend also use one of my rods who repeatedly smacked the tip on the bridge when he went to hookset, and even had a rod get stepped on and not break, though I think in that particular incident the good Lord was just watching out for me.
I don't feel like I am fishing something fragile when fishing one of these modern high tech rods more so than any other rod. I won't say that I am so much better than everybody else because I have never broken a nice rod (lost one, yes!). Perhaps I just have good spatial awareness. What I do feel from these rods is a decrease in swing weight, overall weight (not as important as swing weight, but still nice), responsiveness, accuracy, and sensitivity, and to me that far outweighs the notion that my rod will break simply because it uses less material.
These modern rods are the way of the future, and I'm glad companies are developing new ways to use less resin to lighten things up so to speak.