I have no idea about the claim of a backdoor. But here is the source:
Matt Mackall: "It's worth noting that the maintainer of record (me) for the Linux RNG quit the project about two years ago precisely because Linus decided to include a patch from Intel to allow their unauditable RdRand to bypass the entropy pool over my strenuous objections. "
https://cryptome.wikileaks.org/2013/07/intel-bed-nsa.htm?utm...
The fact that Intel Bull Mountain (code name for Secure Key Technology), and NSA's BULLRUN program share the name "bull" is a complete coincidence. I'm sure.
That doesn’t read like a backdoor or like the community pushing somebody out.