EDIT: A lot of you are reading into the tweet while still somehow agreeing with the overall message. No one is saying we should eliminate music programs or that we should teach toddlers about healthcare plans. The tweet is making this thing called a --checks notes-- joke, that also conveys the message that schools could teach more practical skills that young adults will need going forward.
There's genuinely nothing wrong with pointing out grammar in a normal context, it is obviously awful when you dismiss someone's point over it though which they don't do here.
That is literally what they did
The only point of making a comment like that at the end is to dismiss and shame someone for making a mistake.
Helping someone learn is usually helpful, though perhaps not always wanted. Doing so to call them stupid is not.
According to this exact logic the original commenter did the exact same thing but to the original post.
I don't see it that way, but in what way would that matter?