Technical: DHH is wrong, plain and simple. No amount of defending the decision makes it right.
Community Management: DHH, while not as abrasive as Linus (another thread here linked to a kernel thread), IMO, DHH is (much) worse than Linus. Linus is abrasive and swears and yells. DHH is dismissive and condescending. DHH thinks he has better opinions, more depth of experience, smarter, more insight and generally "gets it" more than everyone around him, including the other maintainers.