This is regarded this as absolutely Haram for both men and women, and I'm not sure exactly why there are so many excuses for it. Let me cite evidence from the source of absolute truth, the Quran.
And hold not the disbelieving women as wives. -- Surah Mumtahina verse 10
O ye who believe! Take not the Jews and the Christians for friends. They are friends one to another. He among you who taketh them for friends is (one) of them. Lo! Allah guideth not wrongdoing folk. -- Surah Ma'idah verse 51
On top of that... Allah also says in Surah Mumtahina verse 4...
There is a goodly pattern for you in Abraham and those with him, when they told their folk: Lo! we are guiltless of you and all that ye worship beside Allah. We have done with you. And there hath arisen between us and you hostility and hate for ever until ye believe in Allah only - save that which Abraham promised his father (when he said): I will ask forgiveness for thee, though I own nothing for thee from Allah - Our Lord! In Thee we put our trust, and unto Thee we turn repentant, and unto Thee is the journeying.
A goodly pattern. I can barely associate my self with Muslims who practice excessive sin without will or desire to change. And the worst Muslim is better than the best Non-muslim. Personally, I believe a lot of us have deceived ourselves into believing we're doing good by behaving all friendly with these non-mulsims and getting all close to them.
The Prophet Muhammad
once said: Only associate with believing folk and only let a god fearing man eat your food.
We're supposed to love for Allah and hate for Allah. It's not good and kind to be all nice and intimate with non-muslims, just as it is the same if you do that to a Muslim who practices excessive sin in the open (Drinking alcohol for example). This only corrupts them further. We aren't to mistreat them in anyway, though we aren't supposed to be intimate with them either. When you condone and accept them, it makes them feel justified and fine with their lifestyle and beliefs... beliefs that will take them to the hell fire, and we fuel it by being impartial about it. People call it care and love, though I call it selfishness, only after the pleasure and enjoyment they give you but hardly considerate to where they'll end up in the future.
also says in the Quran...
O ye who believe! Take not for intimates others than your own folk, who would spare no pains to ruin you; they love to hamper you. -- Surah Ali Imran verse 118.
They also ruin our mode, attitude and devotion towards the straight path. The Prophet Muhammad once also said: Show me your friends and I'll show you who you are.
It's not that they're inherently evil and wicked people, though more that they badly need guidance. Taking them for intimates, saying it's Dawa or something like that is also farcical to me. A lot of us tend to have our own ideas and conceptions of how to behave and act in our lives while they go against the denotations of Quran and Sunnah. No one know how best to run our lives than Allah and his Rasool, though we fill our minds with all these excuses and ignore the truth.
If we really cared about them, we wouldn't get so close to them, laughing and joking with them while they're walking the path to hell fire. I find this sort of behavior very perturbing.
Yes, there are those that have succeeded in converting their non-muslim spouses, though that doens't make it right to go against Quran and Sunnah.
Please forgive me if any of you take offense to this. It's really something that gets to me that so many Muslims can think that way.