As a former bartender, non-practicing lawyer and loyal FT member who accordingly feels no compunction about offering uninformed opinions, I'll offer a few guesses about a few factors that might affect airlines' liability in such situations:

1. Did the airline allow boarding by a passenger who (usually due to inebriation) was acting disruptive or fail to remove the obviously disruptive passenger before take-off?
2. Probably even more important, did an FA provide the alcohol that helped make a passenger disruptive or that arguably intensified the passenger's pre-boarding inebriation?
3. Did the FA take no or inadequate action after being informed of a passenger's disruptive conduct?

Again, these are just guesses, and pretty uninformed ones at that.