"Look at it this way, love. We're already here. If we can't 'sin' here where else can we do it?" Besides, Constantine doesn't like the term. It's loaded with religious baggage that he'd like to give the big middle finger to. It's not wrong to him, to have actively made a decision that the extent of the kinds of relationships he can have with other people shouldn't be defined by where their fun bits are or any other physical characteristics. If anything, everyone else is being far too rigid by having preferences.

"Nothing you can do now can undo the harm you've already done to other people. You're taking this 'sinning' business far too seriously."