Sometimes one spouse outgrows childish habits and wants an adult partner for life. Sometimes people develop gambling addictions. Sometimes people start listening to short-wave radio and think the black helicopters are out to get them. Sometimes people go nuts and threaten to harm the kids. I really don't think we should consider somebody a failure for knowing when to call it quits. If somebody changes careers just before their industry tanks, we applaud their insight and good timing.
As a survivor of sexual abuse, I can see where the GP is coming from. Look at it this way. You're in a loving relationship with somebody you trust with everything: your money, your body, your truck, your kids, your deepest secrets and fears. (OK, I'm a Texan, so truck might be first on that list.) Then you find out he's been lying and cheating for the last four years. Now it's suddenly as if you've been getting raped for four years and didn't even know it. It's not like you would have consented knowing that he could have picked up god-knows-what VD from his little fuck buddy. Not only that, but the perpetrator has 100% access to your money, your house, and can even take your kids if he has a good lawyer. In some states you can't even insist that he leave the premises.
And the whole "blame the victim" thing is every bit as common with cheating/divorce as it is with rape. How many forums have you read where people just say, "maybe if you would have put out more often" or "maybe if you stayed thin" or "you should have known he was a cheater before you married him." In some states, the spouse getting cheated on has no recompense, either. So implicitly the state is blaming the victim, too.
Sure, it's not the most elegant comparison, but it's not totally beyond the pale.
Worst. Hazelnut spread. EVAR!!!!
"Don't tell me I'm burning the candle at both ends -- tell me where to get more wax!!"