Two things. One, if you are a passenger and not a uniformed member of the actual flight crew, do not tell me where to sit. Not to be rude, and I am sure you fly a lot, but I will ignore you at best. If you were to (even jokingly) tell me that I should have moved when you made your announcement, I will respond with a very limited level of humor.

When it comes to moving my carryon without permission from me, consider this. What if you're moving something I own, maybe a computer or valuable piece of medical equipment which can not be easily replaced, I expect you to do so with my express permission. In fact, I would respond much better to the phrase "Can you move your bag" if the phrases "Excuse me" and "Please" are used. In fact, "Would you mind helping me squeeze my bag in, as yours is kind of in the way, but we can both fit if we move things around a bit, please" would work better than deciding that my suitcase is in the way of your bag, and that you should move my bag as it is your desire.