The definition of a yes man is:
: a person who agrees with everything that is said, especially, one who endorses or supports without criticism every opinion or proposal of an associate or superior.
For a start, a good man is not a yes man. Yes men lack integrity, the ability to stand by their values, principles and standards. They have no map or compass. Yes men generally live life through other people’s expectations and that’s not healthy, especially if you’re married to one. Sooner or later there will be problems.
So why is it a bad idea to always agree with everything anyone ever says, even if it’s just to keep the peace?