Ad hominem implies abusive, but abusive does not imply ad hominem. Fair enough. The reason I still think it's ad hominem, is the implication that because RMS is this crusty old weirdo neckbeard legend that doesn't exactly fit in with a bunch of young hip-to-be-nerdy hackathoners, his arguments about Free software (using RMS capitalization) don't fit in with hip and modern web API-using programs. But, of course they do, hence the AGPLv3.
Of course, the implication isn't stated explicitly. Say what you will about that.