They complain about Dockerfiles and have a broken link to some project with 288 commits, without even acknowledging that a Dockerfile isn't needed to build a docker image. It is just as easy to build from a regular old disk image, a chroot, etc. I don't blame RedHat for trying to capitalize on the container frenzy, but this doesn't reflect well on them. Also, kind of expected more from the SELinux Coloring Book.