I am a guy and i watch porn because it's just something sexual i do when i'm not with my gf and i am horny. I don't think less of my gf just because i watch porn. She knows and she doesn't care for porn so we never watch it together. It's harmless. If you do break up with him because of this then that is a bad decision. All guys watch porn.. fact of life. (for most guys atleast.)