People tend to believe that I'm this prudish strait laced
nerdette, at least when it comes to the things I write. Just
because I don't swear or use profanities liberally doesn't mean
that I don't have such thoughts whilst I'm phrasing my sentences!
It is not everyone's talent(?) to come up with
short and sharp insults that are so subtle that most people don't
get the sarcasm until they think back, or perhaps re-read /
recollect the statement over. Then again, some never do.
Of course, there's the standard, "drop dead," variations of
"idiot," "jerk," and the like, but when somebody is really angry it
doesn't always make for an effective comeback.
It's more challenging if we insult / be sarcastic without the use
of profanities... and I would think that the effect would be far
greater. It makes people actually have to think, as opposed to
familiar swear or curse words that would not actually deliver
anything apart from the fact that the other party would know that
we're pissed off.
Put it this way... assuming if I were to say :
"Oh... I don't think you're dumb, but what's my opinion as compared
to thousands of others?"
...and saunter away nonchalantly, is definitely more cutting than
if I just said :
"You're such a c**k and a half!" 
Not only would he be momentarily flabbergasted whilst letting the
double edged meaning sink in, he'd be racking his nearly
non-existent brain for a wittier comeback!
Even in politics throughout the ages, a "well-meaning" insult have
let some politicians have their say and get away with it. For
example, Adlai Stevenson said: "If they were to stop telling lies
about the Democrats, we will stop telling the truth about them" -
now... that's a classic!
Just yesterday while I was having some drinks with my buddies, this
guy came up to me (it would help if he was even remotely
attractive!) and said :
"Hi, I think I've seen you here before. Do you come here
frequently?"
If he was a tad more 'sincere' about it, I would've given him the
benefit of the doubt, but asking such a clichéd pick-up(?) line
whilst ogling and leering takes away any well meaning intentions
that he may have had; So I replied:
"Not if you do..."
and he goes on to say :"Really, ah?"

Oh... by the way, I'm not usually this smart, I'm just making a
special effort today. 