The parent didn't say anything pejorative about those who do things differently. They said "fuck this", and lamented feeling punished by social pressure to be a morning person.

Saying "fuck this" about a submission is pejorative, as opposed to saying "I disagree with this."

I am saying "fuck this" to the culture that pressures everybody to be productive in the early morning and casts judgement on those who have trouble being productive in those hours. No offense was meant to the author, I'm always interested in people sharing their routine advice.

It also conveys a nuance and adds a spark to the response that "I disagree with this" doesn't.

https://www.youtube.com/watch?v=beV0N7lItuQ

You said the pejorative statement was about those who do things differently. Saying "fuck this" makes it clear there's a strong objection to the idea(s) presented in the article, something "i disagree" just wouldn't convey in the slightest. Saying "fuck this morning person" would have been the statement your critique would fit.

I don't think they even said they disagreed. They said it wasn't for them.