As you said, asking a question of the format "Isn't X Y?" is likely to come across as ranty. So why not use a different format: use a title like "Is X Y" or "Does X mean the same thing as Y" or "How is X different (in meaning) from Y"? Those don't carry the same implication that you already think you know the answer.
It's also a good idea to "show your research" on this site, which in the context of a question about the meaning of a word usually means quoting dictionary entries and explaining why they don't resolve your question. This can help show that you have a real question, and are not just trying to rant about some usage that you understand but dislike.
A good way to find some relevant online dictionary entry is to enter your word into the OneLook Dictionary Search and read all of the linked definitions. If you don't find anything relevant, you can show that you did research by saying something like "None of the dictionaries indexed by OneLook Dictionary Search have anything relevant to say about (this meaning of) [word]".
If you are asking a question about some contemporary usage of a word that you think is too recent to be in any dictionaries, you could quote a specific example to illustrate the usage that you want to learn about.