You're not alone in struggling to ascertain the author's tone/purpose with this passage. I used to teach this passage in LSAT class, as the perfect example of a "hard to read" passage.
Part of what makes this passage so rough is that the 1st paragraph is unusually UN-helpful in terms of foreshadowing what the passage is ultimately about.
Also, the sentences that end up conveying the most attitude/opinion are still very subtle about how they do it. In order to read this passage the way the author intends it to be received, you almost have to picture some snobby English literature professor with incredibly dry wit, swirling brandy and mocking the deconstructionists by pretending to be fascinated by their school of thought.
The first paragraph, as I said before, does not give a clear sense of where the passage is headed. You start out thinking that this passage is about linguistics, about how words in a given language come to have new meaning.
However, really that whole intro is just a build-up for the author's first soft jab at deconstruction. As he ultimately makes clear in the last paragraph, he thinks deconstruction is bad because it ultimately dismantles a text. Hence, his little lead-in is just saying that we should have known, with a name like "deconstruction", that "deconstructing" would be its game.
The other attitude-laced part of paragraph 1 is "presumptuously" in line 10. The author is offended that deconstructionists are so convinced that their literary theory is the right one that they presumptuously call their work "theory", as though there could be no other kind.
(A lot of times, a subtle little adjective/adverb in the first paragraph is our best chance at suspecting a negative attitude early on, so be on the lookout.)
The 2nd paragraph still confuses the aim of the passage. Again it seems like we're talking about how new words are created, but the author is really sarcastically talking about how deconstructionists coined the pointlessly complex terms "signifier" and "signified" to refer to "word" and "thing". Once you realize that the author ultimately thinks deconstruction is stupid, you can "hear" this paragraph is actually dripping in sarcasm. The author is explaining the beginnings of deconstruction with masked disdain.
The 3rd paragraph is where we finally get the author's more pointed critiques of deconstruction. He warns us that the name 'deconstruction' conjures images of the building trades, and suggests that deconstructionists think of literature not as organic but mechanical ... authors are not inspired, but
merely assembling raw materials into familiar structures ... deconstructionists take apart the text NOT SO MUCH to repair it, as to demonstrate all its flaws.
All these distinctions are contrasts between what the author thinks SHOULD be the case vs. what deconstructionists think/do.
In lines 46-50, the author contrasts 'criticism', which involves skill/wisdom, with 'deconstruction', which the author finds to be a brutal act of destruction.
Again, I definitely had a hard time getting all this nuance out of my first read of this passage. It's helpful to re-read a passage like this "the way you wish you had" the first time.
That way, we might be better prepared the next time we see one of these snarky Arts/Humanities authors who are too intellectual to just say what it is they mean.
Hope this helps.