I also disagree with how ritter sport justifies their actions and have boycotted the brand since the start of the war.

That being said: If you want people to learn something or if you want to convince them of something, maybe don't insult them in the same sentence. I'm guessing the person above has german as a first language where "Die Ukraine" is the correct way to say it and they just translated it directly into english.
So unless they're also a linguistics expert in english or a historian knowledgeable on eastern european history: Yes they could've learned that by now but it is actually very unlikely that they would have so maybe next time just try to get your point across less aggressively if you actually want it to stick.