I think it is about losing your composure when your secret is revealed. It doesn't matter whether or not other people would consider the secret something significant, it matter that it is important to you.
For this guy, maybe he considered that being forced to prostitute himself in order to...
At this point I would be surprised from anything.
Though at first I thought it would turn out that the "mom" was actually the dad...
Manga has ruined me and I see crossdressers hiding at every corner.