I've seen that type of hostility from non-climbers on the interwebs. Whenever you see a news report of a climbing accident in conventional media, there is often some sort of a negative remark similar to the one you describe. Climbing is seen by some as a useless activity costing tax-payers money and loved ones an emotional distress.
I don't really think the foul-mouthed motorist who yelled at Rob was motivated by fiscal responsibility. Nor, I suspect, was he a distraught relative of Rob's.
I suspect he was merely a beered-up a$$hole of sub-average intelligence who didn't like seeing that someone enjoys a physical aactivity that he is not capable of.