On Rudeness while Driving

I generally consider myself a good driver. I'm not overly cautious, nor am I dangerously reckless. I also consider myself a considerate driver. If someone has their signal on the change lanes, I'll generally make room for them. If someone's waiting for a parking spot, I won't swoop in and take it. And I never pass on the right. So I hate it when people mistake what I consider to be consideration for rudeness.
Yesterday I was driving to work. Sometimes I'll stop at McDonald's for a tasty sausage mcmuffin with no egg. The McDonald's that I usually patronize is at the corner of Alvernon and Speedway. Being situated at a corner means that the right turn lane into the McDonald's is also the turn lane for the intersection. As I was approaching the turn-in, I saw a cyclist ahead of me. I turned on my turn signal and slowed down so I wouldn't hit him. As I moved into the right lane, I checked my blind spot only to see a silver speeding jeep about to careen into me. I got back into my own lane, but as the jeep passed, the woman driving mouthed a very obvious "fuck you!" to me as she sped by. I was a little shaken by the whole experience, but as I started to think about it more, I was pissed off.
First off, I acknowledge that I should've checked my blind spot earlier. But she had come up so quick that I didn't see her before. I was doing something that I thought was right. Cyclists are traffic too, and there was no way for me to speed up and get around him and still get into the McDonald's. I had to slow down. Also, that's usually just a nice thing to do. Its much easier and less scary for everyone if I just put my foot on the brake pedal rather than cut off a cyclist (who's definitely more vulnerable in a crash) and then slow down to make a turn. So braking was really my only option. But this lady seemed to think that the only reason I was slowing down and getting over was to cut her off. She was so pissed that she had to brake that she didn't even think about why I was doing it. To make matters worse, she probably cut off the cyclist in her rage and that was the very thing I was trying to avoid.
I just wish people would think about why other people are acting the way they are. If I'm slowing down approaching a crosswalk, there's probably something in it, so don't be the asshole and pass me. If I speed up and pass you, maybe I need to make a turn at the next light. If I'm slowing down at a right turn lane, MAYBE THERE"S A FUCKING BIKE THERE! Its not like motorists do stuff to deliberately piss off other motorists, as least the great majority of the time. So just hold your horses and think about what someone else is doing and consider that maybe there's a good reason for it before you scream obscenities at them.