There's nothing wrong with taking folk music seriously, we all do, that is why we are here.
I didn't see that his posting was hate mail. Just an observation that you have a very positive view of the definition of folk music. As such, I thought that it was a lighthearted amusing comment.
He could have just as easily made fun of my very relaxed view of what folk music is.
As I said at the beginning, this thread is just for fun, so if you don't want to have fun there are enough serious threads out there for you.