I used to believe this myself. And I'm not saying I am positive that it isn't true still..... but the more I have learned, the more I have experienced, the less I believe men love unconditionally. I think there is a possibility that a needy man came up with the idea that men love unconditionally and women do not. The reason I used to believe men loved unconditionally was that I was married and I stayed with my wife despite the fact that she made me miserable a lot of the time. But through time, healing, experience, self-reflection, and a lot of reading, I look back and realize it probably wasn't unconditional love at all. I simply thought she was the best I could get and I'd never be able to find another woman as good as her, even though she was a total pain in the azz. If I had more respect and belief in myself, I would have let her go and found someone better, or simply went on living my life with or without a "replacement" for her.
Unconditional love means no matter how someone changes or what they do, you stick it through. That's not noble, that's just dumb.