Well I have lived on both ends of this debate now first hand, I will say when it comes to cheating there is no KINDEST way to do it.
There is no good answer to this issue, you can take sides all day, you can say that there was something missing that drove the cheater to cheat.
you can say there is no excuse communication should be there to work it out before that
you can say sometimes the victim does't want to hear whats wrong.
you can say the cheater doesn't love them or that the cheater does love them
What I have found what I have lived is there is no black or white to this question. I have been lied to and found out and its just as painful as being told to my face.
I have also done the same in return and on both ends its just devastating the emotional repercussions of cheating are heartbreaking on both ends.... yes I said both ends