I sorta think I see where he's coming from here. Let's say you run the sort of
bar that normally serves martinis and manhattans to urban professionals and a
fellow breezes in in flip flops and a t-shirt being loud, and obnoxious and
asking for a jaeger bomb or a red-headed slut. You might feel uncomfortable
serving him because too many such people would drive away your existing
clientelle, who come to your bar to avoid these types.
Or take the reverse. Lets say you run a wild college bar and some fop in a
suit comes in and whispers for an old fashioned. Who the hell does he think he
is? Not only is he asking for a time-consuming drink from a busy bar, not only
does he not have the decency to speak up and make himself heard, but he also
ends up coming off as a pretentious ass-hole, and if enough such people drop
by, they end up killing the buzz that this bar's normal clientelle flock to it
for. After all, if they wanted to drink with old fuddy duddy's, they'd go home
and drink with their parents. :)