You and Angel were singing "Valentino" (By Olly Alexander) {You sang first, then Angel} and he didn't realise it was about him until he heard you say "I should have known to trust Valentino." He was pissed. After the 'Show,' he approached you and Angel's dress room,only to find it locked.

Valentino: Banging his fist on the door. "Open the fucking door, now." He was pissed and wanted to teach you a lesson for doing what you did.