Should My Wife Keep Talking To Her Male Friend If She Knows That He Has Been The Main Reason Why We Always Fight?

Maybe instead of fighting with her over her friend. Talk to her how it make you feel. Talk to her without accusing her in some sort of way.
I don't completely agree of her having a male friend, doesn't matter if she needed some kind of suggestion or advice from the opposite sex. If for some reason she needed a male version to give her the wisdom of advice, I still believe that she should come up to you first as her husband or find a therapist that might help her. But then again, this is my own opinion.

Trust is a fruit of a relationship in which you know you are loved.

I'm going through a similar case. My wife has had a male friend for years. Since we've been together we've all hung out on several occasion. He's an ok guy I guess but lately I have been fighting with her over her hang out session with him and his friends..ie her friends. It wouldn't be a big deal except I've intercepted a few texts about him " missing her" and how his day would be complete if she were there. I've pretty much abandoned hanging out with the 2 of them. He may be just her friend but the underlying mistrust and few key texts make it hard to deal with. I guess I question wether or not I have the right to ask her to stop hanging out with him. If we broke it off today he'd be right there to scoop her up. That's just how guys are. All I know is it makes me miserable.

Sometimes, fighting over the fact that she has a male friend, will upset her more and need to talk to him more. Perhaps you should try to plan some sort of activity, the 3 of you have dinner at the house and a movie. Get to know him, and find out if this person is sincere in just having a friendship with your wife. Sometimes, a member of the opposite sex can be a wonderful friend and does not always lead to an affair. Do you trust her. Lack of trust will cause insecurity, and I know that anger is often a result of fear. Fear of loosing her. You may loose her by always arguing about this issue. Try to resolve it as a team, rather than making it a problem between you. Like I say, take the problem, her friendship, and rather than approaching it from opposite sides, be on her side and talk about the issue together

I am in a similar situation. My wife's ex started calling her about 2 months ago. Although he lives abroad, I am very uneasy about it. This is more the case, because he once tried to get her back (before we married). I am 99% sure that is what he is playing on. I do not want to upset my wife and give her a feeling that I am insecure, But it hurts me really deep. One thing I cannot get my head round is that this appears on the outside to be happily married with 2 children. Human beings can be so insensitive and cruel. Surely my wife CANNOT be the only person in the world.

Dontdoit is right. Trust is key in any relationship. You need to trust her.
Try talking to her and then if it just doesn't feel right afterwards and she
continues I don't know what to say. You should go with the positive
though. Remember she loves you why she's with you.