Gomer, to illustrate your point here two pictures of the flare boom at High Island 264. One is 'at rest' and the other picture was taken during an emergency shutdown drill. It did indeed melt the windscreen of an Astar parked on the adjacent crew quarters a few years ago. Both pictures were taken from the landing pad. At that distance (no more than a couple hundred feet) the roar of the flame is deafening and the heat singes your eyebrows. Yes, it is a good idea to give flare booms a wide berth...
P.S. to give you an idea of the scale of the flame: the triangular walkway leading to the boom is about ten feet high.