I don't defend cheating, the idea of going through someone's phone is another argument, but the weight of moral wrong here lies primarily with the individual cheating. The guy looks like a sympathetic figure in the video because he is a clown, you are the lowest of low if you are getting married and cheating on your partner, you should feel bad, but most importantly, you shouldn't cheat.
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Also, women are likely to make excuses for cheating because they are usually in a financial and emotional hole, worst when you throw children in the mix, they don't have the proper outs, so they get trapped in relationships, this leads to people thinking cheating isn't a big deal because there are women that simply put up with it given their circumstances.
Simply put, the guy is trash, the children are fine to trash his as.