smart-alec replies for drivers who harass bikers?

Not to be a downer and not contribute to what could be a funny thread of ideas, but I tend to not say anything.  No need to further upset an idiot and risk them actually taking action on their threats.  Most people with temper and anger issues are just waiting for a reaction out of you as an excuse to do something.  However, I have pulled out my cell to take a pic of their license plate.  That usually gets rid of them.

I was on my bike at a stoplight, in the r/h lane on a 4-lane road on Sunday, off to the right so if a vehicle wanted beside me, there was room. I noticed the left lane was full, but no one pulled up beside me. When the light turned green I went into the intersection, still way to the right and a truck with loud mufflers (or lack thereof!) blew by me very fast, with a finger out the window! I guess he stayed a few carlengths back just to do that on purpose.

Long story short, I thought to myself, "Me thinks thou art a/an (insert noun of choice here)."

No need to inflame an already irate person(s).

+1 x 100000000000000 Complety Agree

x2 for calling police and reporting it.

You can't win and nothing you say will convince them of their error.  A visit from the police will.  Put the non-emergency police number in your phone.  Call and report the incident.  If they later cause an accident, your report could be the deciding factor in whether they are let off as an "accident" or if there's a history of their behavior that leads to them being charged/cited.

I had a pickup truck go psycho on me during a century ride 2 years ago.  Tractor in the opposing lane, and no shoulder, and he was pissed he couldn't pass me fast enough apparently.  Big truck, floored it past me with inches to spare just before a stop sign.  I did *not* flip him off, but threw my arms up in a "shrug/what the hey?" gesture.  He then proceeded to launch into a tirade, and put his truck in reverse ( I was behind him at the stop sign ) and start gunning his truck and jerking backwards.  I immediately unclipped and moved to the side.  Pulled out my phone and called 911.  He saw me do this, yelled "Are you calling the cops on me?".  I said "Yes!".  He dropped an F bomb at me, and then peeled out and drove off.

I got his plates, and gave a description of the driver to the cop that showed up a couple minutes later.  The cop took the complaint and said he was a known local knucklehead and would be getting a visit as well as another flag/note on his record.

Reserve 911 for drivers that are obviously threatening you ( IE, aiming vehicle at you ).  Use the non-emergency number to report aggressive/abusive drivers.

On a slight hijack here - but we stayed in downtown Cincinnati over the weekend for a wedding and I was simply astounded at the number of truly onerous cyclists.  Now granted, most (but not all) were not of the road-bike or tri-bike variety, but I can see how urban motorists can begin to resent bicycles over time.

I saw them swerving in and out of traffic, onto sidewalks, running red lights, and even going the wrong way on one-way streets.  (And most didn't have on a helmet.)

/hijack

Wave, smile, say thank you, appreciate their potential ability to share the road, tell them you hope the day continues to improve for them. 

They'll usually be too confused by the kindness to continue spiralling in anger...