They try to explain it all by revealing a deep, dark secret from his past, but it's a hollow retcon thrown in to try and salvage a character they spent the last 40 minutes assassinating.
I agree with you that this episode is one of DS9's most pitiful and poorly executed attempts. But I do actually think that this revelation about Worf is important. It ties back to Guinan's conversation with him on TNG about why he doesn't laugh. As ill-conceived as the episode is, I do think that the anecdote from his childhood is an important detail in Worf's story.
And this episode does shatter (in a somewhat literal sense) the (imho) bizarre relationship between Leeta and Bashir. (I mean, really, it felt like it was TPTB saying, "Hmm, let's get our most physically attractive male character and put him with a good-looking dabo girl! Ratings!".) And I, personally, like the storyline that comes out of that development.
But I definitely agree that this episode is really not so good as an overall package.
Related, if one has never read MA's Behind-the-Scenes, or better yet, the DS9 Companion
's, entry on this episode, you really should. It's kind of morbidly fascinating how many Murphy's Laws happened during the making of this episode. Sad too, 'cause they had some good ideas.
Also, thing I don't like about this episode: Curzon's "death by jama'haron
". Hate it. Stupid. Uncalled for and bizarre. Really, Dax goes back to Risa for a good time after Curzon dies there? Without ever mentioning it? Meh. Also, we see Curzon dying, but still alive, in "Emissary" when the symbiont is transferred. Death by jama'haron
sounds a lot like a heart attack to me, which doesn't really fit. (Unless it was an infection, of course, but that doesn't sound like a pleasant way to go, unlike what was implied in the episode.)