You can't see nearly enough from the video to determine if the open flame near the propane tank was actually heating the tank to any significant degree or not. Also, the non-shooter in that clip looks to be a good 10-15 feet to the side... maybe a few degrees forward of the sacred "180 degree line", but not in any dangerous position as far as I'm concerned relative to the shot.
They hit on every shot, so I don't think there is any basis to say they are poor shooters, or don't care about developing as shooters... there is nowhere near enough information there to make any sort of pronouncement as far as that goes.
Other than backing off another hundred yards or so, I don't see what the big deal is... no innocent bystanders around, they don't appear to be near anything particularly flammable, etc. Is it the quintisential picture of what some of us like to think of as "responsible gun ownership"? I guess not, but I still think some of you guys need to lighten up. They aren't hurting anyone except themselves if they screw up, and its a free country.
I've shot completely empty propane tanks before... handgun rounds (9mm and .40 fmj) did not even come close to penetrating... they just rolled off, barely even making a dent. .223 penetrated both sides of the tank. Whether this is indicative of the sort of penetration you would get against a full or partially full tank, I don't know. I'd also like to see if you really need a nearby open flame ignition source to light the contents of a just-shot propane tank.