AIO trying to school this guy on what my own sentence meant?

I took a German course in high school and Ive thankfully retained a lot of the information. Unfortunately for me that means that people who only know two words in German (being Nein and Heil) are extremely annoying extremely quickly, and i tend to comment on these peoples comments usually gently telling them why what theyre saying isnt right (specifically this post where everyone is assuming Neun should be Nein, its not their fault, its all they know) but at the time of leaving the original reply i was a little fed up with all of the comments I was seeing so I was being a little snarky. A few weeks go by and suddenly this new guy enters the chat criticizing my usage of the english language. We had and are still engaging in a grammatical battle of sorts (he replied just now to that last comment, ill keep yall updated) and i just want to know, am i overreacting or am i entirely justified in defending my own damn sentence?