Thank you for the replies. I still have several issues with this, though. Ok, let's just pretend for a second that this guy turns over a new leaf and is honest to everyone involved and starts treating women like people... Not likely but we'll just say that's what happens. And say my wife and he start some relationship outside our marriage: I have an obligation as a father to think of my child because (although I'm surely biased in this situation, no doubt) I feel I have to be the rational one and wonder, "What is my son going to say in ten years if this is going on?" And also, I don't want other people (ie. those that did not bring him into the world) being his mother, father, etc. The man I mentioned in the parent post pretty much sees the world and issues (race, politics, relationships, etc) in a completely, diametrically opposite way from myself.
And you all have to admit that when a person that is monogamous enters into marriage, they probably would not have entered into it if they knew that down the road all the vows and feelings that it began with would be discarded, at least at large.
This is me thinking aloud and trying to get some input, as well. It isn't meant to be offensive or upset anyone, by the way.