"Do not do it again" is an order (an imperative statement), not a threat. A threat would be "If you do it again, I'll come to your house with a cream pie and throw it into your face while shouting, 'Mit Schlag!'" Or some other statement that included potential consequences. Moderators are allowed to make imperative statements.
As for whether or not it's insulting, well. What we say in the south is "Don't teach your grandma to suck eggs." Or, to quote Shadow Wizard on your closed meta.se post,
"As for your comment, it is insulting since being a moderator and long time member, that other user obviously knows the rules. No need to throw it in his face. Besides, we can't control what offend people. For all I know, you might be offended if I'll show you picture of a cat. So you can flag it, while the other user happens to be a moderator - he didn't suspend you or anything, just removed what he considered offensive (and wrong) comment."
Offense is in the eye of the beholder. You're certainly offended; do you have a right to be? Who's the judge of whether you have a right to be offended or not? Are we going to take a vote, or does the right to be offended require consensus? If we take a vote and the majority decide that you have no right to be offended, will you magically stop being upset and say, "Oh, well, that's all right, then"?
Michael is a person with the same right to be offended that you have.
The implied question seems to me to be, "Are moderators allowed to be human beings, or must they be perfect emotionless automatons who never get offended or make mistakes?" If you find any perfect people, let me know and I'll vote for them for moderator in the next election. In the mean time, I think Michael does a good job.
