I could critique the word choice by saying that using that word suggests that the author is being dishonest and deceitful. Manipulative, while technically correct in the abstract, is not necessarily accurate when one considers that the intent might merely to have been to provide context. At the same time using the word manipulative brings along baggage you might not intend. Manipulative implies intent on the part of the person doing the manipulation.
I could also critique your use of the word in another way (and,as it so happens, the way you used it). Keep in mind, this is still technically correct.
Your use of the word manipulative is deceitful. Your use of the word suggests you know intent, and your use of the word attempts to do what you accuse the the original posters of doing: attempting to manipulate the reader by framing the argument as one against deceitful, manipulative, and by extension, distrustful young people. Words are powerful, and your word choice demonstrates that, at the very least, you either have no clue, or your a vile, deceitful individual.
Both methods of critique are valid. One addresses the problem, the other addresses the person. Both are unbiased and fair criticisms, but only one is polite.
We, as a community should strive to encourage. This is not any where close to blanket approval or being yes men. But do NOT for a minute think that good, helpful criticism is simply unbiased and fair. It is not.