Part of their massive appeal is that these sports constantly walk on the thin edge between brilliance and disaster.
The fans, corporate sponsors and especially the athletes know this. It's just a part of what they do.
Still, something in me screamed, the death of a 25-year-old isn't supposed to be the result of a sporting contest for our entertainment.
A week ago, millions of people tuning in to ESPN watched Moore essentially kill himself on live television.
They didn't know it at the time because Moore, with assistance, walked away from the wreck, caused when the snowmobile's front skis hit part of the landing ramp as it was coming out of a backflip. Moore was sent flying over the handlebars to the snow-covered ground. The speeding machinery crashed into his defenseless body.
Initially, it was announced that Moore, who had stayed down quite a while, was taken to the hospital to be treated for a concussion.
What wasn't known was that the impact of the snowmobile had caused internal bleeding around his heart.
Moore had emergency heart surgery the day after the crash, but the cardiac injury led to complications involving his brain. He clung to life for a week before he died.
Why does this seem different to me?
Is it just my unfamiliarity with these sports that make me believe the accepted risks seem more stupid than those taken by 200-to-300-pound men who crash into one another at full speed to chase an oblong ball? Or how about the people who drive cars at 200 mph just inches away from other cars?
In the 18-year history of ESPN's X Games, Moore was the first to die in competition.
But why is my initial reaction, "Geez, I can't believe there have not been more."
I mean, really, who thinks you can survive attempting a backflip on a 450-pound snowmobile? But one person does it, then another and the one after that until it ultimately it becomes a routine trick.
And then it is time develop the next one that will be even more insane.
I think part of it for me is that these sports are still so new and I'm not desensitized to the danger, the way I am with football, auto racing or hockey.
We know there are inherent risks, some of them life-altering, with those sports.
But after decades of watching those sports, we know the dangers have just about maxed out. There are no new innovations or skills coming to football, hockey or boxing that would make them more dangerous.
In fact, all moves are in the opposite direction. It's all about making sports safer, sometimes to the detriment of their overall appeal.
I am not saying that the people involved with extreme sports are not concerned with the utmost in safety standards.
Fans of extreme sports are not more ghoulish than those of more traditional sports.
No one wants to see what happened to Moore. Yes, we have an appetite for danger, but only the most depraved mind tunes in hoping to see a serious injury or death.
I think it goes back to original observation about what is the limit: How far should they push the envelope?
From all indications, Moore wasn't unqualified to try his fatal stunt, having performed it before.
This time, unfortunately, he just made a mistake. And although a mistake in just about any sport can result in injury, this time Moore died.
But why does it feel much deeper to me than that? Why is my initial reaction to say, "Stop this"?
I know of football, basketball, hockey and soccer players who have dropped dead while playing or practicing.
Boxers have been beaten to death in the ring and some of the most skilled auto racers ever have died in horrific crashes.
I accept that as part of the game and know that it is rare. I know death in extreme sports is not normal either - not at the level that these athletes compete. Maybe it's because these extreme sports haven't yet reached their final frontier of possibility.
So I say it's insane when I see some teenager shoot 30 feet into the air out of a halfpipe to do twists and flips on a skateboard or a snowboard; or when I see some free climber risk a fatal drop just to reach a summit; or when I see a young man trying to do a backflip on a snowmobile or a motocross bike.
And when they have turned what I had previously considered the impossible into the probable, I ask myself: "What will they try next? And how far will they go before somebody kills himself?"