I know that all of us love our Bullets, and I too would rather have the guard take the blow rather than the bike. But lets also prefer our legs and bodies to the Bullet, all of us, in thinking through the consequences of any accident. Between damage to my leg, and damage to the bike, the choice is a no brainer. If it comes to that, we can always buy ourselves a new Bullet.
Quite honestly, if you fall while riding the bike, it is very, very unlikely that the bike will fall over the leg. In case of any fall, the first thing that will happen is that you will get unseated, and then separated from the bike, which, in 99% of the cases, will be a good thing. And if the guard comes in the way of that separation happening, I would rather not have the guard.
I think Kiwichick has the best approach to the use of the guard, as she has set out in an earlier post.