Sure, but the CPU has to perform correctly on general-purpose computations so it's not too likely that, for example, the multiplication instructions occasionally give wrong results. Detecting cryptographic code executing in the CPU and subverting it is hard in general, but quite easy if you have a special instruction used only for the purpose.
There are multiple special-purpose security instructions; AESENC, for instance, or even PCLMULQDQ, which was added to speed up GCM. Which ones should we keep and which ones should we jettison?
Since AESENC and PCLMULQDQ are meant to be deterministic - including their timing - it's rather harder for Intel to subvert them in a way that's not detectable than something like RDRAND.
You've overshot, though. The solution to what you're describing isn't to remove RdRand from the Linux kernel, it's to entirely give up. This is not a defense of the change.org request.
