Certainly
Airlines have done much worse things...
Amadis of Gaul
In the age of the 24-hour news cycle, I doubt UA will "suffer" much at all.
However, in the previous referred to 2008 affair:
https://en.wikipedia.org/wiki/United_Breaks_Guitars it is reported (and cited):
It was widely reported that within 4 weeks of the video being posted online, United Airlines' stock price fell 10%, costing stockholders about $180 million in value.