Am I being reasonable?

My partner (male) was abused by men during his childhood. He told me he decided to explore his sexuality due to his body getting aroused by anal simulation. Whilst he was exploring his sexuality he cheated on me (he met up with a gay man for drinks) he has concluded he isn’t gay and doesn’t have any sort of physical or sexual attraction towards men. What do I do now? Do I see him as a victim or do I leave him for cheating and meeting someone behind my back?