A man marries a woman and runs into a bunch of emotional turmoil with her. This could be because his ideal of her is now crushed - he has to deal with the fact that she is an individual, that she actually poops, and that she has her own little MAN living inside her, who can be something of a bastard at times. Or, this may be because he happened to marry a screwed-up woman. (Usually, it is a combination of the two, plus him being a jackass). Let's say she turns out to be an emotionally unstable nut - or just has some personality disorder. And, no matter WHOM she married, she'd end up unhappy and in a dysfunctional relationship. Well, certainly the husband, by now, is thinking she's nuts - and a whore and all that.
One day, the woman is crying, and she calls her friend, a man - possibly a jerk. Man number two CAN'T BELIEVE THIS! How DARE man #1 cause this wonderful ideal goddess to CRY!! Well, see, man #2 is using this "goddess" device in order to fight away man #1, the husband. It's a ploy for his own personal conquests. Going to war for the Queen. Men feel driven to fight and compete with each other, and the Madonna/whore complex is their excuse to do this. (It's not so much that they genuinely care about the ACTUAL woman).
Then man #2 ends up marrying the woman, becomes convinced that she is a bitch, and the process continues... Both the males and the female(s) have been socialised into playing out this little dualistic dysfunction. And they learnt it from their own parents. Mom was so absolutely giving and selfless - but damn her, she controlled every aspect of life!
And, females also project a similar dualism onto men: All men are liars, bastards and jerks, "except for MY man! He is the toppers! He is the knee of a bee!" Because, well, dad was so wonderful all the time, except when he came home drunk. Then he was a bastard and a liar, always making Mom cry... It's a childish thing, this dualism. But it is partly necessary, to make life interesting. The more interesting, (i.e., BDSM), that it makes life, though, then the less that INTIMACY or RESPONSIBILITY or JOY are cultivated - replaced by a pathetic emotional dependency.