Before he even discusses his individual points the author gives his definition of "bad," and the reason the other approaches are "bad." From the introduction:
> Let's talk about a few cases where either REST or HTTP (which is clearly RESTful in its design) solves a common web development problem.
> so they make up a partial solution that solves their given case but doesn't jive well with the way that everything else works
The problem is if you don't follow those constraints, but still call your system REST. The meaning of the concept is rendered useless by so many people abusing it without understanding what it means.
It's not saying various practices are "bad," but that they don't conform to REST or the principles laid out in the HTTP specs.