I agree with you that adults need to take ultimate responsibly for their actions. But despite the best of intentions, we all make mistakes.
I also think that there is responsibility for Bar Owners when they know their patrons are over served. If Bar Owners feel strongly enough to remove them from their establishment, they should make sure this patron has someplace safe to go, rather then turning them out on the streets in a very compromised vulnerable state. An easy solution would be to call LE.
If I understand this situation correctly, this young man was not even able to hold himself in an upright position and was badly stumbling when he was ejected from this bar. A responsible sober adult should have stepped in, whether that was a Bar Bouncer or the Bar calling LE.
This World is not perfect, but we certainly should all step in for others when we see them in any compromising situation.
Maybe there is a lesson here, if you ever see anyone struggling, don't just walk by. Maybe helping a person is as easy as a 911 call.
JMO