You can't make a thread with advice and expect everyone to become saints all of a sudden. These things will always exist in a community, and you can't correct everyone at once by doing this. What is more practical and understandable is to point it out when you find someone crossing the limit when they shouldn't be. Whenever I see someone with a higher rank getting unnecessarily rude with a newbie or a newer member, I point it out right there, and say that they should do it because it's not appropriate, and I believe that's the right way to do it and not by creating a thread.

I would also like to mention that someone who is a part of a community where they have to put out their thoughts publicly for the whole community to read and share their opinions about, they need to understand that they aren't always going to get sweet responses, and they will need to learn to handle harsh ones as well. Sometimes, some people will throw constructive criticism at you and you might find that being rude, but you need to take out the positive out of it, and then respond to the same response in a matter that should make the person on the other hand realize that you didn't take what they said as an offense but you learned something from it, and that might change their views about you.