Issue could create rift!!

Hi, everyone!!
I am in desperate need of advice and guidance for what to do. Any help is greatly appreciated.
I apologize for the long wall of text, but I put in all necessary details to help people understand my situation. Thanks for your time.

I am in my late 20's, have a solid job and a healthy relationship. My girlfriend (let's call her MK) - of nearly 4 years - and I recently moved into a new place that we intend to make our home for a good chunk of time (next is the house). We get along great, have small bumps that are always talked out and we are starting the very serious talks about engagement rings and children as well as fixing our finances to prepare for all of this. I love my girlfriend so very much and I'm already in the process of designing her ring and planning the proposal.

I point all of this out so that you understand how much she means to me.

She and I have friends (DL is the guy, Dolly is the girl) that we've known prior to us knowing each other - let alone being together - and those two friends dated and split up prior to us meeting each other. Now, I've known DL for a few years, but I've known Dolly for the last 9 and she is probably my closest female friend that isn't MK. She is as close to me as my little sister (and that's pretty close). MK has known DL from school, too, but didn't know Dolly prior to meeting me, so her "loyalty" has always been to DL. And it's assumed that mine is to Dolly.

To make a long story short, I have had a rather large disdain for DL due to his womanizing nature and to how his break-up with Dolly affected her. I put on a brave face and a smile whenever MK would have me hang out with him. Eventually, the disdain subsided and there was never a situation where DL and Dolly had to be anywhere near each other. Things seemed to be in a nice, safe bubble.

Well, Dolly came to visit me yesterday and opened up to me about something that she has been keeping to herself for nearly 7 years. She came out with the fact that DL had forcefully raped her numerous times in their relationship because he didn't want to wait for her to be ready to surrender her virginity. He would choke her, hold her down and do it; all this while being drunk every time. This would happen a few times before, to protect herself, Dolly would start to let it happen and not fight it. Eventually, he broke up with her for someone else and she was "free" from his selfishness. Over the last few years she has kept it a secret from everyone. The reason she has kept it from me is because she knows of the friendship that MK and DL share and she didn't want to risk a rift in my relationship with MK.

That's where I ask for help. MK doesn't know yet about this series of rapes against my best friend by her good friend. I'm in absolute fury mode right now as I try to think reasonably about how to approach this. MK is very supportive of rape victims and never creates excuses for the victimizers, so I doubt she will "side" with him. However, I fear that MK will try to "keep the peace" or pretend that things can work out in this situation - she always tries to find the good in people - without someone's friend being alienated. I have a severe hatred for sexual deviants and I will not buckle down from my best friend's side. That scares me. What if MK says that she won't remove DL as a friend or, worse, tries to say that Dolly may be creating a lie or something to that nature? I wouldn't know how to react, how to deal with such a feeling. Besides Dolly's very real pain, I am terrified of this guy being around MK and what he might.... attempt.... if they are ever in a situation where he can take advantage of her.

I want him gone. I want him out of our lives - Dolly's, MK's, and mine. Is that fair? Do I have a right to stand by this belief? What should I do if MK doesn't want him gone? How do I let MK and DL be friends without it hurting Dolly's recovery and developing friendship with MK? Please, I know this is long, but I need help on this. I don't want this to be a rift between me and the love of my life. Please help.

Thanks,
C

You must approach this not with anger but with concern. Tell MK that Dolly revealed something disturbing about DL, but leave everything about what you what like to do to him for it, or that she needs to ditch him as her friend. You must discuss this objectively, without judgement for you don't have all the facts and this would be very difficult news for MK to take in as well. Confronting DL is not the right thing to do, but suggest to Dolly to get counseling because what has happened to her traumatic. Sad to say she missed her window of opportunity to have him charged so there is no use in perusing any retaliation for his actions. Give this information to MK, and let her decide the fate of her relationship with DL....keep your opinion out of it unless MK asks you. This will be a true test to see how, you two as a couple, will handle a serious situation as this. You will have to trust your future wife's judgement, but of course be open to work through this with her.

Thanks for the advice!
Happy to say that, prior to the reveal this weekend, Dolly has already started seeking help with the situation. She says that she loves her life and everything in it, except for that one situation which has ruined intimacy for her, hence why she is seeking help. I'm proud of her for that.
MK already knows how I feel about DL, so it may be rough trying to keep my now inferno-level hatred for the guy to myself, but I will take your advice and try to keep that to myself so MK can come to an objective decision herself.

Well I hope that MK will take your feelings into consideration as well on this. Hopefully MK will know that between you two is a partnership especially now with marriage pending. Marriage is a totally different ball game, you are thinking for two not for yourself.