Then there are the random labelers. "Lesbians!"
I've always thought of responding "Very good!
Trees! Cars! I can play too! Stop sign!
Garbage cans!" but I usually just say "This
is New York. Go back to Idaho. You don't
belong here." A good answer that leaves
them speechless is, "That's right! Can
you handle that, or do you need someone
to talk to about it?" Another one I've
thought of is "Ohhh, no, not
'lesbians--'
muffdivers,
perverts,
bulldaggers,
butch dykes,
rugmunchers,
queers, 
twisted
manhating
sicko freaks,
cuntlickers! 
and how 
'bout all
you queens!
cocksuckers!
buttfuckers!
fairy-ass 
faggots!"
etc., by this time shouting
and thereby attracting the
attention of any passing
dykes and fags who might
want to join in. This is
called co-opting, and
used right, it can
embarrass people.