I wish the authors had focused on the design of DUAL_EC_DRBG, since that's a more objective and compelling response. Mathematical features of the standard make very little sense without a backdoor, and the original article provided essentially no justification. Rather, it attempted a distraction by pointing to alternative configurations and standards.
The authors might also have focused on the NSA's consistent refusal to deny that it backdoored DUAL_EC_DRBG. It is difficult to see what intelligence harm could come from such an acknowledgement. After the Heartbleed issue went public, for example, the NSA quickly denied that it had previous knowledge.
Unfortunately, the authors focus on NSA skullduggery and misconduct, citing primarily to non-expert (and semi-sensationalist) reporting. That's not very surprising, since Bruce Schneier is an activist critic. (As is Green, I'm not familiar with Heilman.) I think it undermines their case, though.