I like the satire and parody in Hackmaster -- the stuff that takes elements of 1E AD&D and cranks them up to 11 -- Gygax's ostentatious language and authoritarian tone, the baroque and occasionally mutually contradictory rules, the gratuitous sex and violence, the kitchen-sink deliberately anachronistic approach to fantasy, and especially the antagonistic players vs. DM mentality (that all players are rules lawyers who will seek out any loophole to screw up the DM's plans because they have to because the DM is a megalomaniac who delights in nothing more than belittling and humiliating the players). This stuff isn't necessarily funny to someone who'd never played 1E AD&D, but to someone who knows it well, who had the books damn-near memorized as a kid, who can spot all the references, a lot of it is absolutely hilarious, and the fact that it was all clearly done by fellow enthusiasts motivated by love rather than spite (they couldn't skewer the game so effectively without having themselves played it for years (decades even) and having the books virtually memorized themselves) makes it even better. It would certainly have been possible to do a mean-spirited parody of 1E AD&D (and I've seen more than a few over the years) but that's not what I see in Hackmaster.
What I don't like about Hackmaster, however, are the jokes that aren't referential, that aren't specifically satirizing or parodying 1E AD&D, and are expected to be "funny" in a more straightforward manner (the example that stands out most in my mind is the race of gnome-titans with their "groin stomp" special attack). To me, at least, the vast majority of this stuff isn't really funny, some of it is just embarrassingly lame, and it spoils the appeal of the game.
While I agree that Hackmaster-without-humor would be pointless, I do wish the focus of the humor was more on satire and parody of 1E AD&D and less on lame "yuks."