This sentence doesn't make sense in English. It should read something like:
"Why do you talk like that?"
"Why do you say that?"
No. I think that it's right.
No it's not, it makes no sense in English. "Why do you say like that?" makes no sense.
Like that?/Như vậy. Nothing is wrong.
"Say like that" isn't correct. "Say that". Please remember that English and Vietnamese words do not always transfer 1:1. The two languages have different grammar. "say like that" has no meaning.
Ok. No meaning in English but it has meaning in Vietnamese.
Actually it should be removed from both languages. "Tại sao bạn nói vậy?" is just fine.
As you know, "Like that" different "that".
Sometimes in this course, the English sentences will be phrased in certain way in order to clarify the use of individual words in Vietnamese. Please accept the odds, and focus on how the sentence in Vietnamese is formed.