Skip the finger and the attempted vehicular homicide and you have a point.
You do know that if your timing's a bit off, or if the target of your rage happens to get a bit ticked off in return and guns it, your cut-off can result in smoking ruin for you, the other guy, and probably a bunch of other people who were unfortunate enough to be on the same road as you, right?
Just make the pass and go about your business already. Personally I move over if someone faster comes along, unless doing so is going to seriously impair my ability to, say, pass the slow semi I'm approaching.
Crude example:
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[-grr80-] [-me73-]
-- -- -- -- -- -- -- -- -- -- -- -- -- -- --
[{SEMI}][{65mph}][]
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(speed limit 70 - distances compressed for space)
This is not the right time for me to merge right; I'm not going to brake hard to under the speed limit so 'grr' can drive his preferred speed. It is, however, a good time for me to plan to pass quickly so I can eventually let 'grr' by. Some people get nervous at this point and drive 68, which is both annoying and dangerous.
Did you know that many vehicles are calibrated wrong? Thanks to those annoying roadside display-radars that are placed in order to scare people into driving the limit, I've found that 30 on the speedo often means 27 or even 25. The slow guy you pass may think he's already speeding :)
You know if drivers were more considerate...I wouldn't be having an existential meltdown..........right now.