Is cheating sometimes acceptable?

I know a man who has been married for...I'm guessing quite a while.  They have three children and he's a GREAT guy...except for ONE BIG exception....he is a  serial cheater.  Now, I wrote a blog a week or so ago about cheaters.  I can't stand when people do that.  I don't think that there is any reason for it.  Well, a while ago I was talking to this man about it and he told me that, in his country, it is a way of life.  He is from Africa.  If that's the way of life from where he grew up....does that make it okay even though he's living in the United States?  I have been pondering that issue and I honestly don't know the answer.  I don't think anybody does.  It's just a fact of opinion. His wife has no idea about the other women that he is or has been with.  Well at least she didn't.  They are now starting to go through a divorce.  It's a tough thing to talk about.  Should he be penalized for something he grew up with and learned from his community?  I think so.  I don't think anybody should be able to have an excuse for hurting someone they supposedly "love."  Just like the old saying "If someone jumped off of a bridge would you do it too?"  It's the same concept.  If someone cheats does that mean that you will too?  It's just an excuse!  It's not like the people in his African country forgot to teach him right from wrong.  He KNOWS that he is doing something wrong otherwise his wife would have known all along! So, what do you think about this subject?  Is it acceptable because of the circumstances...or is it just an excuse???