What did the Chinese man say when someone asked him if he got St. Patrick's Day off? Irish.
I don't know what exactly you mean by this?
Asians can't say the letter L. It's a fact you know
While some Asians perhaps struggle with certain words, you would too if attempting to speak their language rather than your own. There's no real reason to put down anyone from speaking multiple languages, even if you believe it is just a funny joke. It does nothing but create a stereotype that harms.