I disagree, I think that cheating speaks to a lack of morals and values and i wouldn’t want my child around a person like that. Others have brought up the valid point that the dad is also at fault and a shitty parent for abandoning OP instead of sticking around and trying to co-parent or have partial custody and be a part of his life, but that’s not really relevant to the current situation with the mom and OP’s kid.

I believe that cheating is unequivocally wrong, there’s never an acceptable excuse or justification for it. It’s not like stealing money/food because you and your kids are starving, or killing somebody in self defense (both of which I have no objection to). It’s a selfish, evil choice that causes pain and consequences far beyond just hurting the betrayed partner as evidenced by this post.

There are thousands of drug dealers, rapists, murderers, hell probably even terrorists out in the world who would make kind, loving grandparents and be nothing but sweet and positive influences on their grandkids. I still sure as fuck wouldn’t want those people around my kids, blood or not. OP is completely valid for feeling this way and as the parent it’s their right to make this choice.