You say social media is unforgiving, but is it really? In the short term, sure, but you think this will have a lasting impact on United? Social media is fickle, if nothing else. It will move on to something else soon enough, and completely forget about this incident.
Here's one example: me. I fly pretty much weekly for work, paid by the company I work for. The online reservation system my company uses allows me to select from various airlines and times. Guess which airline I am not picking? I was flying United, so they lost weekly airfare from at least me.
Yeah. Maybe people will forget about the incident soon if nothing happens, but they're now primed to think United is even scummier if it ever does something similar in the foreseeable future.
Social media is more than fickle.. it amplifies the breadth (spreads to lots of people fast) and depth (make it look worse) of incidents. Millions of people have now seen that brutal United video, and remembered that it's all United's fault. Tomorrow when there's another United incident, albeit minor, regular and social media will amplify it - one more hit for the consumer. Each incident in isolation will be forgotten, but the bad taste remains. Look at what's happening with Uber, Bill Oreilly, etc.
[1] Pepsi: That was the biggest PR blunder of the week, year maybe.
United: Hold my beer.
Sean Spicer: LEEEEEEEEEERROOOOOOOY JEEEENNNNNNKINS!
Fickle indeed. Hopefully United learns from this incident, tho I think it's unlikely
There's also an episode of It's Always sunny in Philadelphia (S12E04) where they talk about the 24 hour news cycle - which pretty much sums up social media unforgiving nature