I don't understand what Nagizuka did wrong. Can someone explain me that part?

He basically made him out himself.

Basically Nagizuka tricked Makoto into admitting that he was gay by asking if he has a boyfriend in a discreet way so Makoto would answer without thinking. It may not seem like that big of a deal since Nahizuka's bi, but coming out is a very important thing for people, especially in a place like Japan, and outing someone as gay is extremely rude.

Lol yea mine's like the shorter version of this but same thing. :)

AHAHAH yeah i thought maybe they wouldnt know what outing meant as a term (▰˘◡˘▰)

Thank you