The feeling of intense embarrassment after one realizes they have constructed their sense of self on false premises.
At age 13, Matt was what you would call wapanese. Having never confronted his self-misconception for what it was, he channeled his existential embarrassment into hatred of others who reminded him of the way he used to be.
SARAH: baka! ^^;
MATT: congrats you're weeabo garbage
AMY: Matt, don't be malicious to Sarah as a form of compensation for your inability to deal with anything that reminds you of when you were 13 and deluded.