Nice Nimbin, you ventured into another territory where I have experience... Martial Arts. I have 9 years of Tae Kwon Do experience and have been practicing my own style since I quit that discipline when I was 14.
Your analogy does not work here because Martial Arts is about controlling your own body. In snowboarding, you are relying on a board to keep you above the snow and moving downhill.
You are trying make it seem like all of us are trying to say that Women can't use Men's boards. This is not the case. They absolutely can. What we are trying to say is that there are boards specifically made for them that will most likely make their riding more enjoyable.
Even in Martial Arts now and in history, there are weapons made specifically for females. Female ninjas, Kunoichi, used cat claws which were long fingernails made of iron. They also used to dress as Geisha and used those paper fans that had blades attached. Sure, they used male weapons too, but these female specific weapons enabled them to take full advantage of being a female.
Sorry for my rant... I love debating
As for why and how a board is designed for lower center of gravity... Simple... the flex is more forgiving on female boards. This is due to women generally being weaker and having a lower center of gravity. Having a lower center of gravity means you have less leverage over the board which coupled with the fact that they are generally weaker, makes it that much more difficult to flex the board.
Think of it this way... A see-saw with a higher mid-point will teeter at a wider angle than one with a lower mid-point. Flip that see-saw upside-down and you have yourself a male vs a female snowboarder. The male having a higher center will have more leverage and will be able to flex and lift their nose/tail higher than a female on the same board.
In the end, we are both right Nimbin. You are correct in your assumption that females can certainly use mens equipment. You are however incorrect about female specific designs being purely marketing hype (a level of marketing factors in regardless of gender). Women don't need women's specific boards. A really athletic and experienced female snowboarder needs it even less. But the option is there. Just like women can wear a guy's jeans, but they have the option to wear girl's jeans which are more fitted to their body shape.
Some reading:
http://www.winterfeelsgood.com/winterfeelsgood.php?section=sports&page=buy_w_board_tips
http://www.the-house.com/portal/why-buy-women’s-specific-snowboard-hardgoods/
Also, you say your wife loves your board. I dare you to buy her a good quality womens board fit for her measurements and then tell me what she thinks. You have the female riders on these forums telling you first hand they stick to womens boards.
I am surrounded by female shredders in my work and I only know one who rides a mens board, the Skate Banana. However, she loves good womens boards like the Feelgood as well. She is a park rider and is really good so she is one of those athletic experienced riders I mentioned above. One fact does remain though, all of these ladies recommend womens board to other female riders. None of them go around telling a female rider to buy a mens board.