As I've seen it Sport (Olympic) fencing is
basically the same as it was when it was a real combative art. Yes, it may seem suicidal but that was the whole point... to get that thrust into a vital faster than your opponent. Yes, true with the blunted tips of today those who spar are less likely to be more mindful of the effects of their opponents sword on them and thus perform those "suicidal moves" Langenschwert spoke about.
However if the body pads, gloves and face shields were off and the tips needle sharp and the edges honed to razor fine... many of the present day gold-medalists would probably not be alive today using their award-winning techniques. Heck this would apply more-so to the Silver and Bronze medalists as well.

But since there's no fatal risk involved then one can get more reckless and move into an opponent's attack whereas before they'd wait for the right moment to thrust-home.
It's almost like Olympic TKD is different from real defensive TKD in the same respects.
Good point - the same theory is still there, but some of the caution has been "suspended".
We should probably define what we mean by "fencing" as well as what we mean by "martial art".
The term "fencing" is from "de-fence". So, by definition "fencing" is a "martial art."
Plus, it's so broad that it's like asking "Is Karate a martial art?" Well, some people study it as a "real world" defensive system, and some study it as a sport.
Most people think only of the foil as the weapon of fencing, but there is also the epee, the saber, the schlagger, the rapier, the smallsword, the cutlass, the backsword (or hunting sword), the broadsword, the longsword, etc. ad nauseum. (Similarly, there's Taikwondo, Tang soo do, Wing Chung, Ninjutsu, Kenpo, Chun-kuk-do, etc. as well.)
They are all considered "fencing." For instance, I fence with a rapier/schlagger, and a longsword (usually called a "bastard sword".) There are sport arenas and applications, but we study historical methods which were actually used at one point in history to kill people.
So, is the question about "Olympic-Style fencing". That is, the foil, the epee, and the saber?
As Lang. said, the foil is a training tool for a smallsword. The theory behind the foil is dangerous when you switch the foil for the weapon it was meant to train for. However, the smallsword never really got a reputation for being particularly deadly.
I've trained under a saber fighter, and let me tell you, his technique is definitely martial. I wouldn't want to face him in a live-steel duel for any amount of money or honor.
I don't have any experience with the epee, but I know it does not have right-of-way rules, which is more true to the practical application of dueling. I understand it was popular for "first-blood" style duels in the 19th century, so "stopping power" and killing blows didn't have as much focus.
To me, "first blood" duels are a dangerous form of sport fencing, since you "score" by drawing blood, and the first one to score, wins. (Of course, if the blood you draw comes from an artery, or the heart, well . . .)
When the general public asks me about the rapier fencing, I tell them we study fencing "as a martial art", but that's more about where our focus is, to distinguish it from points-based focus, but I won't tell a sport fencer that what s/he does is not a "martial art."
I would like to play with them though, you bring your quick foil/epee, and I'll bring my long, slow rapier. I'll bet we would both learn a lot. But I don't know right-of-way rules, so don't expect me to follow them
