Yamaha blaster bent bumper
 

A lot of years since I worked on a blaster but all the utility Quads I work on have bolt on bumper assemblies.

I go for the "Desperate Dan" (British comic book character) method of tying the bent bumper to something solid (usually the back end of a stationary big tractor) with a slack rope, and setting off backwards, cutting the power as soon as the rope goes tight. Gently at first, then repeat with increasing speeds until it pulls the bumper back to where it should be. You can pull one side more than the other, and if you overdo it and break a mounting off, you weld it back on.

Almost always over do it that way. I chain the back of the quad to a tree and use a come-a-long hooked to the bumper and my truck. It's a lot easier to control.

Even if you can end up getting the large dent pulled out like that (its surprisingly difficult to get it looking good), your bumper will still have signs of the crash and will still be weakened. I would suggest pulling out the skid plate (how they suggested) and just buy a new bumper.