Put it in context
Standing at that fence, or trying to hang onto that fence while an aircraft is taking off, is like a lot of other activities in which there's a risk you'll fall or be knocked down. Like skateboarding, rock climbing, trail bike riding, skiing, etc.
99% of the time when one falls, one picks up, dusts off, and moves on. Occasionally one gets a bruise, sprain, or broken bone. Or a knock on the head and a concussion. With extreme rarity, the knock on the head can be fatal, as it appears to have been in this case.
It can even happen stepping off a curb hailing a taxi.
Is it "stupid" to try to hang onto that fence behind a jet? I dunno, how much value do you get from the fun / thrill / Instagram video relative to the risk? Is it "stupid" to go skiing, rock climbing, trail bike riding?
Nobody can really answer that question for anyone else. It's only stupid if you don't understand the risks or choose not to think about them.