My friend is in love with a married man. How do I get him to leave his wife?

you don't...statistics are that men hardly every leave their wives. why should they...it's a perfect situatin for them. It's the wives who usually leave the husband.

Men who cheat on their wives are very shallow, deceptive men, greedy too. A married man with a mistress invariably have had or currently have multiple mistresses. They generally need their wives for dependence and stability, if not for the money. Men have had mistresses since the earliest human civilization. And 99% of the time they are throwaway pieces of soft candy. Plus, it's usually the wife who leaves because of infidelity. Men don't like that, and they leave their harem behind pennyless and forgotten. Tread lightly here and don't get involved, tempers do flare, people get hurt one way or another