I read a lot of this thread. I had no idea how many people really believe random ninja invites are ok! This isn't opinion guys, its the way its been for the last decade and a half.
Etiquette develops over time. In MMOs, part of the established etiquette is that it is considered rude to invite without asking. That is a fact in every sense of the word.
The guy on page one that posted about no tell invites while waiting for the same spawn had it 100% right. Thats what MOST mmo vets expect.
OP, I approve of your crusade against the invite ninjas. Good luck! From the look of some of the replies, you are going to need it.