Biker filtering

[Justintime]

Was in traffic when this guy in front of me went to change lane, the guy in the other lane stopped to let him in but he didn't quite have room yet until the car in front moved up a bit.
A biker who was filtering traffic and was not even in sight when this manoeuvre was happening rode straight up to the side of the car in front of me, started revving his engine and cussing at the guy calling him names etc.. and how it was his right of way blah blah.. THEN he proceeded to stay on the guys side when he finally got in and rev his engine then cut him up for about 30 seconds then tore off at an amber light so the guy would get the red.
I always wondered, is filtering a right or a privilege? Seems to me the biker was completely in the wrong and a massive tool at the same time?

 

[Justintime]

Sounds like stationary traffic on a dual carriageway, car in front of the OP in his lane wants to change lanes, sees half a car gap to move into which leaves him straddling both lanes. Filtering biker comes up the middle of the 2 lanes (as he's 100% allowed to do, OP) and sees numpty sat there blocking the way.

Biker probably over reacted a bit, but then the car driver probably shouldn't have tried to push into a gap that wasn't there.

The biker "wasn't even in sight" but that could just mean the OP hadn't seen him, and the car in front could have pulled out a few seconds before biker arrived, that we don't know.

Anyway, yes OP, filtering is 100% legal. And bikers rev their engines not only to show anger to car drivers, but also to let them know they are there.

I guess i worded it a little wrong. My 'right or privilege' question meant did he have the absolute right of way and everyone must clear a path for him or was it a privilege to do so but accept that the way may get blocked and he had to wait for a safe gap.
The biker was definetly not is sight as i heard the engine from a long way off, the other car had already partially done his manoeuvre when he came on the scene about 10 secs before his engine was even audible.