There are a three conflicting principles at play: 1) your rights as a groom; 2) your long-term friendship; 3) the fact that you now have a family.

My best friend took himself out of my groomsmen party because he got mad at me for ditching out of golf. He said some pretty mean things, about both me and my fiancée. We've been friends since 4th grade and this is the first time we've really had a falling out. He wont be himself again unless I apologize for what I did and admitting he's right. He is married to his wife. I'm engaged to my girlfriend and we have two kids. He doesn't seem to get the lifestyle difference. Should I swallow my pride and make mends? Or make sure he realizes (which he wont) that our lifestyles are different and things do in fact come up at terrible times, like before golf.

Excellent question. There are a three conflicting principles at play:

Principle 1: You're the groom, so everything should break your way.
Principle 2: Your friendship is more important than a short-term spat.
Principle 3: Your new marriage is more important than your friendship.

Let's go through each in turn.

Principle one: Based on the information you've provided, in the most literal sense, clearly your friend was out of bounds. You are the groom. For any events surrounding the wedding--the bachelor party, the rehearsal dinner, or any buddy-activity even tangentially related to the ceremony--the group should defer to you. If you want to play golf, they golf. If you want to hunt elk, they hunt elk. And if you need to reschedule golf, they reschedule golf. Or even if you had to bail at the last second--which sounds like the case--they should understand and be accommodating. That's the deal. And all of this should be clear as day even before you throw your children into the mix, which clearly gives you a pass.

Also, here's what puts it over the top. Rarely, if ever, is there an excuse for your friends to say "pretty mean things" about your fiancée. This is unacceptable. She's the woman you love, the woman you will be with for the rest of your life-your friends need to respect this.

All that said... keep in mind Principle Two: your friendship is more important than any short-term spat.

You guys have been friends since the fourth grade. While this disagreement is ugly and regrettable, you have enough in the bank to get past this. Right now tempers are high, the drama is high, and you're both (probably) feeling pressure from your respective partners. Get past this. So while yes, even though you are in the right and he is in the wrong--again, based on the info you've given us--nothing will be gained by a long, drawn-out pissing contest.

Your instincts are right. Know that you have the moral high ground but apologize for skipping out on golf, apologize that things turned ugly, apologize for offending him. You want him back in the groomsmen party. (Speaking of, it is a BIG deal for your friend to actually extricate himself from the groomsmen party, leaving us to believe that there's more to the story than what's in your question...)

While you should be the one to broach the subject, apologize, and initiate the peace negotiations, keep in mind:

Principle 3: Your new marriage is more important than your friendship.

This you already know, as you (understandably) passed on golf to attend to you father-responsibilities, which obviously come first. You know this, but your friend needs to understand it. So when you apologize to him, convey that he's a very, very, very important part of your life...but your kids come first. Your family comes first. Even though he's pissy and huffy for whatever reason, he'll have to understand this. If not now, eventually.

Good luck with the conversation-not fun. Just remember that you did the right thing by missing golf and that, once you smooth this over, eventually things will be (mostly) back to normal.

-The Plunge.