Well, rant, rant, go ahead. Flying is hard, and there is always someone annoying and inconsiderate. Just last night on flight from FRA I had someone moving my bag in the overhead just before departure, even though there was lots of room..and silly fellow got really testy with me when I asked him to refrain from moving my bag (from flat to sideways, where it would get scratched by someone's buckle or bag...). Stay calm and carry on.
I think you're well within your rights to ask for some courtesy and consideration when someone is shifting gear trying to find a space in the overhead bin, but "refrain from moving my bag" seems a bit much. It is pretty annoying when people can't figure out how to put their rollerbags in wheels-first so that more than 2 bags can fit in a bin.