Daniel W. Rouse Jr.
In the case of an on-ramp, through traffic has right-of-way and should be doing exactly that, unless there's room for them to maintain speed while still letting the merger in.
Period. He should never slow to let someone in if he can possibly avoid it (unless it's a lane reduction, in which case he should let in exactly ONE merger, at the last possible moment).
Sloths can f***ing sit there until after rush hour, or learn to speed up.
Match the speed of through traffic before even signaling to be let in. If you must punch the gas to do that, do so.
If you're behind a slowpoke on the onramp, drop behind him early so that you'll still be able to get up to speed during merging.
If it's an on-ramp -- never demand to be let in. Never force your way in, regardless of speed. Right-of-way fully applies at the intersection of the on-ramp with the highway, and through traffic has it.
Wait until nearly the last possible moment to merge, so nobody pbuttes you on the right.
If it's a lane reduction, and there is stopped traffic in one of the lanes but not the other, move over to block the open one as soon as you can, thus protecting your place in line and that of everyone already stopped.
On the merging car 100%.
An additional scenario: Some freeways have what I call temporary lanes (an on-ramp becomes an additional right lane, which then becomes exit-only at the next off-ramp, typically 1-4 to 1 mile later).
During rush hour, buttholes sometimes go over into the temporary lane to pbutt the lined-up traffic in the through lanes, then want to merge back in before the exit. I believe in never letting them.