whynotaboutism
Whynotaboutism is the study about "Why not" sentences and how people use it. It is the same thing as whataboutism but instead of "What" there is "Whynot". Also if you want to increase your vocabulary, my friend defined what is "Whyaboutim".
Dialog:
Gay: I am gay
Straight guy: Why are you gay???
Gay: Why not???
Straight guy: What do you mean?
Gay: Go learn Whynotaboutism studies, idiot.
Gay: I am gay
Straight guy: Why are you gay???
Gay: Why not???
Straight guy: What do you mean?
Gay: Go learn Whynotaboutism studies, idiot.