It’s exactly as long as it needed to be to explain everything it explained, and it is a completely dry comment with no real tone at all, the “rudeness” is of your own invention.

Ironically, “Firstly you could read user names before going off” is by far ruder than anything I wrote. Also, you’re assuming I’m the one who downvoted you–have you considered that maybe your tone earned that from someone else, maybe?