Lots of baseless assumptions there. For one I've seen the exact same problems at speeds significantly below the speed limit - the problem is the speed differentials between different types of drivers, not adherence to the posted limit. When you get right down to it the limit is an arbitrary construct, flow dynamics are not. If you want to be safe, help maintain the flow.
As it happens I despise mob mentality, but I do care about flow. Humans can fairly reliably be predicted to behave in certain patterns, you can talk all you want about what they *should* do, but if you want things to flow smoothly you need to plan in accordance what they *will* do. Anything else is asking us to be something other than human in order to conform to *your* idea of how the world should work.
As it happens one of my primary goals when driving is to promote flow. Sometimes that means driving faster/slower than the speed limit to stay within the flow, often it means consciously resisting the apparently instinctual "herding" behavior that creates over-dense traffic clumps that can't adapt to disruptions efficiently. And occasionally it means intentionally disrupting the traffic behind a traffic snarl for a few moment so that it has a chance to sort itself out.
Recently for example I was on the interstate and witnessed a bunch of vehicles, including a semi, merge into the fast lane to let a big line of people on at an on ramp. Before the semi could pull back into the slow lane an aggressive driver squeezed in from behind him, then another, and before you know it traffic is backing up and becoming a serious snarl, the fast lane is merging right to squeeze through the gap, with the result that the slow lane is slowing dramatically and a serious parking lot is beginning to form behind us. So my turn to pass the truck finally comes, and because someone has to do it I slow down and block the gap so no one else can pass him and flash my lights once he's clear. I get a couple angry honks in the process believe me, but 30 seconds later the semi is back in the slow lane, which is rapidly climbing back to the 70 it had been, and the fast lane is rapidly climbing back to the 80+ posted limit. Flow is re-established and I'm free to fall back and proceed to cruise at a comfortable 70 with the rest of the relaxed crowd. It doesn't matter what "should have" been, reality is as it is, and our efforts bear far greater fruit if we work with that fact rather than against it.