That sounded very accusing grace like rain. Of course I said something. In which case he proceeded to tell me how it didn't matter if she was a Christian or not, he said he's had sex with a lot of Christian girls and they all begged him and screamed "yes" while he was having sex with them...
I think my answer is the best, beat the living $%#! out of him and as I'm standing over his half conscious body whisper in his ear "this is where you rethink your life."
Hi triple-seven, I can understand that you have heard this, and you feel the need to protect your friend. And first off I do want to praise this commendable reaction to a shameful comment about another person, treating them as an object, I don't want to discourage you from reacting to that evil way of looking at another human being. However I think you really need to take a step back, first, listen the wise counsel you are getting from brothers and sisters in Christ here, when it is said speak up and say that that is a shameful way to talk about someone else (and I know this can be hard, right now I'm remembering all the times I stay quiet at work and it is something I really need to repent of and find ways to challenge such statements in a loving but firm way).
Secondly, if you believe that she might be deceived tell her, but in the end she is in charge, and whether you beat this guy up or not, you cannot run her life for her. You should act in love towards her (and I might add towards this man to, don't accept his sin and shameful attitude, but embrace the person) which means giving her the respect as a adult and child of God empowered to make her decisions on such things, and the Holy Spirit gives her discernment in such situations. If she is truly like you say she is, she won't fall for his false lines and certainly not him, and you can't be someone who would make her decisions for her, that robs her of her humanity, which is what Jesus died and rose to give us back in it's fullness.
And I think you really need to listen to those above, your emotions over this girl are causing you to lost all objectively, you litterly thinking of beating another human being to near death to force him to not think about attempting ask a person out (even if it is to just sleep with her in such a way, he is not going to be hiding this), and this is going to get him to change his attitude and see the call of Jesus to repent and follow Him?
No you really need to step back from this girl now, your emotions over her or overidding any rational judgement you are having in this situation, and you are trying to run her life as well, if you love step back, be there for her as Friend and as a brother in the Messiah, you are not her husband and you do not have the right to run this siltation for her. That isn't love, that's manipulating control.
For your sake, hers, and even this man at your work, step back please, take a deep breathe and turn to God to give you strength and discerning judgement to act in a restorative and constructive manner in this situation, bringing the love of Christ and His wisdom into this.
So I'll finish it off be say, for all involved, you need to step back and now, you are way to caught in over your head in this, please listen to the counsel of your brothers and sisters here, and please go talk to your pastor or a mature Christian you trust over this, because I think you also need someone to come alongside you and help you through this, and please turn to God and ask for Him to give you peace and clear mind in this situation.
God bless you, and keep you from destructive paths my brother.