One of the fundamental differences between RP and BP thinking is that TRP understands human nature and it's nuances and works to use this knowledge to improve our lives. TBP likes to paint things as black and white, lumping as much as we can into this giant "equal"
bliss (read misery).
Men and women are fundamentally different in almost every way. We are two - opposite - halves of one whole called humanity. More specifically, we're two halves of one whole that is a married couple. We're a team. We can and should compliment each other on an individual and societal level. To do so we need to overcome certain base temptations and instincts that may cause us to be at odds with one another.
Biologically, a man can father many children with many women simultaneously. A woman however, can usually only carry one baby at a time. Twins are an anomaly, triplets are even more rare and more than that is super rare. Even a woman who carries several babies at once, cannot come close to a man who can sire dozens of babies at once.
Likewise, male sexual desire is for quantity, to have as much sex as possible with as many women as possible. Female sexual desire is to select one single mate of the highest quality possible/available.
It's natural to be tempted to cheat. This is true for men and women for different reasons and in different ways.
A man who commits to one single woman, is denying his biological drive to spread his seed to as many women as possible. Therefore, it's only natural for him to be tempted to have sex with every sexually appealing woman he'll ever encounter. He may choose not to act on this temptation for a multitude of reasons, but the temptation is there nonetheless. If your husband says he only has eyes for you, he means that he diverts his attention away from women who pique his sexual interest as to not get fought up in temptation. Or, he's saying that to keep your insecurities at bay.
A woman who commits to a single man is fulfilling her biological drive to choose a single mate with whom to procreate. Branch swinging only exists when she thinks she encountered a better mate or when she's unhappy with her current mate and seeks out a better mate.
Another differentiation is how men and women view sex. For men, sex is a need. For women, sex is at the core of her existence as a woman. Men do sex, women are sex. This idea is discussed more in depth in the linked post. I'll just point out one example where this can be seen. A woman being raped is treated as a more horrible act than a man being beaten to a pulp. Why? Because sex is at the core of womanhood. Taking sex from a woman touches a lot deeper than being beaten for a man, no matter how severe.
Therefore, cheating is different for men and women. Men have an urge to cheat that is a lot less threatening to the marriage. A man can cheat for years without compromising his marriage. In fact, men often cheat as a way of getting their sexual needs met so they don't have to break up the marriage! Women OTOH, cheat because they have one foot out the door. Women cheat as a form of branch swinging.
When committing to a single partner, men deny their biology and women fulfill theirs. Therefore, a man will have much more temptation to cheat than a woman can comprehend. OTOH, when a woman is tempted to cheat it's a lot stronger because her temptation is fuelled by her desire to branch swing.
When a man has extramarital sex, it doesn't break the marriage. When a woman has extramarital sex, it does break the marriage.
Before the brigades swarm in I'd like to reiterate that this post is about understanding human nature. At no point did I excuse cheating nor did I imply that it's a good or moral thing to do