I’m a native English speaker. Honestly… who cares? We can still understand them just fine. Do you speak four+ languages like they do? I studied a second language for 10 years in school and barely remember it. I self-studied a third for a couple of years and it’s HARD. What in the world do they have to be guilty for? Being way better at being multilingual than the average native English speaker?
I obviously care. There is also nothing wrong with having pet peeves. Zero people need to agree with what my pet peeves are allowed to be. I see this dumb mistake all the time and that's not really related to the linguistic status of this one individual.
Sure, have your pet peeves. That’s perfectly fine. However, making someone feel bad about it and implying they should feel guilty, when they’ve already made a huge accomplishment in learning another language, isn’t. You’re not wrong, but you’re still an asshole.
I would disagree with your assessment of this. If I implied they should feel bad, it was for guilting me with information I couldn't have known and wasn't at all personal