Does that really say DD-WRT in particular is a threat? I take it simply as saying DD-WRT is the poster child.

While I like DD-WRT, if you can flash DD-WRT you can flash anything, and arbitrary code breaks all possible chain-of-trust models.

The FCC has a long history of moving for more restricted hardware as a way of regulating the airwaves, one of its chief jobs. As a ham & commercial radio operator it drives me up the wall, but I understand why they do it.