I don’t know exactly where the amount of male bodily harm I would have to suffer comes to be something as bad as rape, but my rough typical mind fallacy estimate is having a leg broken, which I would rather have happen than be cuckolded. There are, in fact large lists of bad things I can say with very high confidence that I would rather have happen to me than be cuckolded.

It is a betrayal which people take seriously. And this whole “How dare you” shtick bugs me. We can compare the values of dust specks in the eye to decades of brutal torture, and our ability to do so doesn’t make us bad people.

Men can have kids out of marriage, sure, but social mores, cultural expectations, and loyalty/cuckodry concerns provide enough incentive to marry for kids.

divorce rate: http://www.divorcerate.org/divorce-rates-in-australia.html
child rate: wikipedia
kids in marriage rate: http://www.aph.gov.au/house/committee/laca/Famserv/chap2.pdf

The biological damage of raising a child that is not his is much more than a rape victims because at least she is investing in a child that is half hers…. if he never figures it out and all his children are impostors then then he is as biologically dead as if you had killed him.

Biological harm isn’t actual harm (though it is predictive of how harmful something will be experienced as by the victim).

Consider a long-term fraud that costs the victim their livelihood, something that took many years to build, and then consider a violent assault from which the victim eventually recovers physically. We consider the latter more reprehensible; we sanction the offender more forcefully, blame the victim less (people avoid reporting fraud because they’re ashamed to have fallen for it; this isn’t a problem with aggravated assault), and in general consider it to be a greater crime.

If, when sex is added to the equation (sex-based fraud, sex-based violence), your perception of the relative severity of offense changes, isn’t it possible that it’s due less to majestic principles of philosophy, and more due to a propensity to consider violence done to female bodies to count less, and fraud perpetrated on male egos to count more?

While I agree with you that I don’t think less of a man who has been cuckolded, historically it has been considered shameful.
http://en.wikipedia.org/wiki/File:Order-cuckoldry-ca1815-French-satire.jpg
This picture shows cuckolded men growing horns. In fact, I once heard that it is where the whole make-devil-horns-on-your-classmate thing in photographs came from.

Historically and culturally, that’s still a very provincial viewpoint, at least as far as the “shameful” character of a man’s being cuckolded is concerned. As Paul Veyne writes in A History of Private Life concerning the Romans:

A woman was like a grown child; her husband was obliged to humor her because of her dowry and her noble father. Cicero and his correspondents gossip about the caprices of these lifelong adolescents, who, for example, might seize upon the absence of a husband sent to govern a remote province in order to divorce him and marry another. These women’s antics nevertheless had real consequences for political relations among the nobility. Needless to say, it was impossible for a woman to make a fool of her lord and master. Cuckoldry (as we know it from Molière) was not a part of the Romans’ conceptual universe. Had it been, Cato, Caesar, and Pompey would all have been illustrious cuckolds. A man was the master of his wife, just as he was the master of his daughters and servants. If his wife was unfaithful, the man did not thereby become a laughingstock. Infidelity was a misfortune, neither greater nor less than the misfortune of a daughter who became pregnant or a slave who failed of his duty. If a wife betrayed her husband, the husband was criticized for want of vigilance and for having, by his own weakness, allowed adultery to flourish in the city — much as we might criticize parents for overindulging or spoiling their children, allowing them to drift into delinquency and thus making the cities unsafe. The only way for a husband or father to avoid such an accusation was to be the first to publicly denounce any misconduct by members of his family. The emperor Augustus detailed the affairs of his daughter Julia in an edict; Nero did the same for the adultery of his wife, Octavia. The point was to prove that the man had no “patience,” that is, connivance, with vice. People wondered whether the stoic silence of other husbands deserved praise or blame.

Because deceived husbands were aggrieved rather than risible and divorced women took their dowries with them, divorce was common among the upper class (Caesar, Cicero, Ovid, and Claudius married three times), and perhaps also among the urban plebs.
Juvenal tells of a woman of the people who consults an itinerant soothsayer about whether she should leave her tavernkeeper husband to marry a secondhand clothing merchant (a prosperous profession in a time when the lower orders bought their clothing used). Nothing was more alien to the Romans than the biblical notion of taking possession of the flesh. Roman men did not hesitate to marry divorced women. The emperor Domitian remarried a women he had divorced, who had subsequently married another man. For a women to have known only one man in her life was considered a merit, but only the Christians would undertake to make such fidelity a duty and attempt to prohibit widows from remarrying.

Here’s a starting point: the size of the martial arts/self-defense industry that caters to women. The overwhelming reason, when you ask such women carefully and cut through the rhetoric about exercise & fun, is that they fear abuse and sexual abuse such as rape in particular.