Many times in my life I have seen and heard people say "his wife probably beats him" or "he's a wimp because his girlfriend polices everything he does" largely as insults. It's very troubling to hear this sort of talk. It implies that male survivors of abuse are weak and should easily be able to avoid abusive relationships based on their gender alone. It is completely ludicrous to assume that males are "wimpy" because they are committed to an abusive partner.
What many people seem to disregard when they make rude comments towards men in abusive relationships is that abuse is not always physical, but it is always mental. The abuser will wait until their significant other is completely committed to the relationship before starting the actual abuse. Most victims don't realize what is happening until they already feel trapped and unable to leave the relationship. They feel obligated to stay or have been conditioned, in a sense, to feel like they are always at fault, rather than their abuser. It's because of this that they stay and continue to try and "fix" whatever their abuser claims is broken.
From personal experience helping a close friend in an abusive relationship, I can attest to the strong feelings a victim may have towards his partner and the relationship. He came to me about his situation, telling me how horrible his significant other is. I listened and told him my perspective on his situation and voiced my disapproval on how she treats him, but I never put him down. What would that prove? Would it "open his eyes" to the fact he doesn't deserve her? Would it somehow make him feel better about himself even though I would be tearing him down? No, it would do neither of those. Instead, it would make him feel as if his experience has been invalidated and as if it didn't matter. He might feel like he has absolutely no one to confide in. Most importantly, he would likely feel like I was criticizing him the way his girlfriend does, which is not at all how one should want to make a victim feel.
The best way to handle a situation such as this is to just listen. Give them some advice, but in no way be judgmental and tell the person if he needs to "man up" and leave. Offer support, but never force your advice on him. Take into consideration that the victim trusts you enough to come forward with how they've been feeling and keep in mind how much strength it would have taken to do so. You always have to remember that an abusive relationship has nothing to do with determining masculinity and everything to do with being manipulated.
Source for the statistic in sub-headline: https://www.safehorizon.org/get-informed/domestic-...