The issue he is referring to is the grsecurity has a history of allowing breaking patches, allowing bad code, attempting to upstream patches in chunks without splitting them up to make the process easier, and then complaining that their patches are being ignored.
> Grsec makes the kernel more secure by breaking it.
No, their patch set includes many different exploit mitigation techniques, and reduction of the attack surface.
> I could make a crappy patch that breaks networking and market it as a security feature because it "prevents intrusion"
You could, but this has nothing to do with how grsecurity works.