Most statements which are sufficiently deviant (from cultural norms) are assumed to be jokes by default. This is a way of protecting everyone from admitting that serious disagreements exist.
For example, if you say, "Thank you so much, you've persuaded me and I've learned a lot. I will completely rethink all my values and take on board the moral values you've shared with me." that reads as likely sarcasm because it would be much more rational than typical people in our culture.
And if you sound significantly less rational than the typical person, it again doesn't read as serious. For example, "I hate you for trying to use logic to share ideas with me that you think would help me. I'm very mad that you could be so arrogant as to think you could know anything useful to me. Did it ever occur to you that I don't want to think?" People will assume someone doesn't really mean that and is just making a joke, perhaps an exaggerated parody to imply the other guy is wrongly treating him like the person in the parody.
Statements which are reasonably normal are taken at face value, but statements which are deviant are frequently not treated as real statements in the usual way. This is a way of denying the existence of deviance and generally suppressing disagreement and pretending it doesn't exist. It's a strategy which helps people irrationally refuse to consider many disagreements and criticism.