No, they don’t become kafir as becoming kafir is not an easy thing to give! There are conditions to be fulfilled and obstacles to be removed first!

If they said this out of emotions and this is what they believed to be right, they are wrong but surely not kafir.

There are many people (even practicing people) who talk about Islam without knowledge, even though they know it is haram to do so. What is the ruling if happens that these people say something which they think is correct but in reality is wrong by consensus (and the matter is not from the fundamentals of the deen or the ilm ad-daroorah)? For example, many practicing sisters say that Polygamy is only allowed in times of war when women are helpless. They say this out of emotion and they know it is haram to do speak without ilm. Do they become kafir by this since they said something wich is clearly wrong (even though the matter is not from the fundamentals of Islam)?