The Bible allows for divorce. It really seems like divorce is THE answer. BUT, Jesus also said that the law for divorce was because of the hardness of man's heart. Whose heart? The husband's heart, the wife's heart, both their hearts? Isn't that a case by case thing? And bigger question, what if God keeps a spouse's heart soft even when being cheated on? He really does that sometimes. God softens our hearts in unusual ways.
That's why I don't usually tell people to walk. (I have. I have when I believe there is physical abuse or there might be polygamy -- the spouse might very well be married to someone else at the same time.) My heart goes with leave the cheater. It really does, but that's God and the person asking's call, not ours.
God answers this question for anyone asking him and willing to seek his answer. This isn't a matter of us telling what to do. It's a matter of God telling what to do. It's a matter of trusting God, not anyone else.
We should be promoting that, not promoting our hearts.