> Ad-hominem is where you use qualities of the arguer as disproof of the argument.

Right, which is what he didn't do. "I don't like Rails because DHH has an ugly hairdo" would have been an ad hominem. In this case, he is disagreeing with the idea itself.

No, that would have merely been an ill-informed opinion and a non-sequitor. One can feel however one wants about a subject and for any reason and still not commit a logical fallacy because feelings are a-logical. For an actual fallacy, we need actual premises: "Ruby is good," "Rails is bad," etc.

An ad-hominem is even more specific. The premise must be disputed because of the arguer. So, if DHH makes statements about Ruby or Rails, and one argues that those statements are false because of DHH's hairdo, then that would be an ad-hominem.