Bob, I totally agree!
I regularly get the 'argument' about hand luggage, coats/papers/shoes on ground etc... I've found that when boarding passengers pointing out to the ones sitting in the exit rows that they are, and all bags need to go up top & please review the card even if they've read it before... generally as the line is moving quickly and other pax are watching they don't argue. Helps 'prepare' them for the crew briefing them on board
Now, I just smile sweetly and explain that actually despite appearances, these seats are not designed for leg room but for an escape route in an emergency and as such must remain clear.... they seem to pay attention at that bit.
With alcohol... common sense applies. If I think the pax are getting a bit merry I explain that sure, they may have another drink but to do so we'll require them to change seats in which case they can continue with the drinks (within reason)