got a guy like that on friday. passed me too close right before a 4 way stop. "Forgot" to stop and got a big one right on his windshield. guy had to notice it, but he followed me for about 8 blocks after that without passing, so maybe he got the point

Two words: snot rocket

I was riding down the road today and this truck getting ready to make a left stops, giving me the impression that he is waiting for me. Not wanting to keep the guy waiting I stood up and started pedaling as fast as I could so I could get by him as quickly as possible... as soon as I took about 10-15 pedals he guns it and makes the turn...

I had to slam on my brakes and skid across the road, just barely missed T-Boning him...

Now I don't know if he did that on purpose or he changed his mind.
I didn't say anything but I gave him a dirty look and when he seen that he stopped and stuck his head out of the window to play tough guy... Amazing he can stop for that but not to let me go by.

I had no problem if he would have turned right away, but he gave me the impression that he committed to waiting for me to go by and then did that...

Was I attacked?

It's probably a good idea in future to not try to do them such favours. As you've seen, they rarely see fit to repay it.

Ride as normal, but watch them closely. Don't assume they've seen you until you see the whites of their eyes. If there's any doubt they've seen you, take more of the lane, and maybe back off the power a bit.

In the meantime, if you can recall the details, get the number of the truck driver's company and let them know of your experience. There's really no reason he couldn't have waited for you to pass, other than pig ignorance.