You absolutely, postively DO NOT want to grab a big handful of front brake. Here's why not.
First of all, unless you know, absolutely KNOW, that the guy behind you is (a) far enough back to avoid you, and (b) paying attention and (c) gives a shit if he kills you or not you run the risk of getting a ride on the grill of his truck, or whatever. Even if it's just a little-bitty car it's gonna hurt like a sonofabitch when he hits you. Second, when you hit your brakes the front end dives, and when you hit your front brake it dives a lot, and when you hit your front brake hard, it dives almost to the bottom. There are a couple bad results from that.
The steering geometry changes drastically, resulting in much quicker steering. It will be very unfamiliar to you just at a time when you probably want to make a quick change in direction. In fact, it may be such a drastic change the front end will want to "tuck" under and dump you when you try to make the cut.
The second effect is just as bad, maybe even worse. Not only is your suspension going to be fully compressed due to weight transfer to the front wheel, but your own, personal, upper body weight is gonna be shifted forward as well, with much of it on the handlebars. Now with your springs fully compressed, what's gonna happen when you hit that bump?
Sport, it's gonna be just like hitting it with a rigid front end. Those two skinny little downtubes are gonna take that hit and maybe bend as they try to absorb it, and there's a real good chance your rim is gonna be trashed. The shock will transmit itself up those tubes to your arms, probably bending the handlebars, and maybe damaging your arms, even breaking your elbows or dislocating your shoulders if you are dumb enough to lock 'em.
When you hit that bump, the front wheel is going to rise, just as surely as the sun tomorrow. Normally, the springs would soak up most of that rise, leaving everything else relatively undisturbed, but now they can't 'cause you've got the brake clamped down tight and the springs fully compressed.
What happens now is that everything on the bike forward of the rear axle (which at this point anyway, is still on the ground) is going to start skyward. And it's not gonna just go up 4" or whatever size the bump is. It's gonna go up maybe a foot or two, until gravity takes over from inertia and starts it back down. And while it's up there, the back wheel is gonna take its hit. Since there won't be much weight on it though, the springs there ought to be able to cope, and just give the back end a little kick UP while the front end is airborne, and get you a real sky ride, landing on the front wheel with the rear probably still in the air.
Guaranteed, you're gonna be one shocked, confused guy by the time the wheels make contact again. Maybe you'll still be on board, and if you are, here's what you got - speed that's pretty much unchanged from the time you hit the bump, a front wheel that goes ka-thump, ka-thump over its dinged spot as it rolls along on a tire that's probably flat, downtubes that may not have the wheel pointing anywhere near the direction you're pointing the handlebars; handlebars that aren't pointing anywhere near the direction you want to go, arms that might be pointing straight down 'cause the shoulders don't work, and a head that just ain't up to this any more.
Better you should just use your brakes cautiously to get slowed down some, then get off 'em completely before the strike. If you can't avoid the object entirely by making a cut around it, get the bike pointed as square at it as you can, get some weight off the front end by sitting back a little, relax your elbows, arms, and shoulders, and ride it out. You'll probably make out better than you expect, and surely better than if you grab a fistful of brake. And if it happens, and you get through it, stop and check the scooter over anyway.