I Don't Understand

Explain this one to me, smart Internet friends.
I get road rage. I do. I know how it is to sit behind a moron who won't move, even though the light has been green for a minute and a half already, or behind someone trying to turn left, even when the sign says "No Left Turn." So I understand how tempers flare and red lights are run and swerves get more sudden and dangerous.
And the longer the commute, the worse it can be.
So tonight. I'm driving home from work. Just as disgruntled as the next car. I have learned that - contrary to common sense - it is actually faster to go through the residential neighborhoods than to take the freeway, so I'm in a long line of cars waiting for the blessed green left turn signal to come on and a guy from the opposite direction stops in the middle of the block to turn left, across traffic and into his parking garage. He presses the button and, sure enough, a gate in the apartment building five cars up from me opens. But the light turns and no one leaves even a smidgen of space between them and the car in front.
Having driven this route every day for a year plus I know how long the green arrow will last so I don't sweat it. I'm not making this light, so I pause to let the guy go across my lane and into his apartment. He doesn't look like he believes the opportunity, and I can't blame him, so I gesture across my windshield that he can go.
He sticks his hand out his window, flips me the middle finger and doesn't go. I am not sure what that's all about, so I wait and gesture again; he can go.
He gives me the dirtiest look and then revs the motor and screeches left and into the garage.
What was that all about? Was I inadvertently being rude?


This is me and that was weird.