No disagreement here. I saw a wonderful discussion recently by a researcher at Mentor Graphics about 2 things: VLSI design hacking and low level interconnect hacking. Things we call "hardware" and just assume are designed securely.
They are not. The hardware designers at the chip and board level know little or nothing about security techniques. They don't work with systems people who build with their hardware to limit undefined or covert behaviors.
Systems people in turn make unreasonable and often wrong assumptions about what is hard about hardware. Assumptions about what it won't do, in particular.
We need to treat hardware like we treat software. Full of bugs, easily compromised. There are approaches to reliability and security that we know, that are tractable. But to apply them we need to drop the fictional idea that hardware is hard... It's soft.
The principle of least privilege is one of those. The end to end argument should be applied to bus protocols like CAN, for the same reason.