Do you think this was serious?

Because they honestly believe that their answer is the right answer. Such people often back up their beliefs with literature and knowledge from people who believe in the same thing and therefore, their knowledge base is rather limited (rather like religious freaks). Or perhaps they are surrounded by weaker individuals who always give in to their arguments, allowing said person's ego to inflate further, when really, all they want is for him/her to shut the **** up! Therefore, it is only serious if you allow it to be...don't! You should only care for the words of people who are important to you.