Monkeys in cages are not known for their altruism.

Today - I was riding on the shoulder of a 2-lane (one direction) frontage road.
The motorist passed me in the leftmost lane, then veered onto the right shoulder (curbed) just in front of me; then took the freeway on-ramp from the left lane.
Seems like intentional harrassment to me.

I see people drift into the bike lane when there is no cyclist there, so why does the situation change to malice?

I'm beginning to think that other drivers' drifting has nothing to do with me.

I've been driving too much lately and I can't get over how many people just drift into the oncoming lane for no reason. It was bad enough one day when I was in my pickup and the guy in front of me was doing it. Then I noticed in my rear view mirror that the driver behind me was doing it too. It was a straight road. But it really annoys me to be going around a corner and be met by somebody coming toward me in my lane, even of only a little bit. It's been a daily experience. For some reason I don't notice it when I ride my bicycle, perhaps because nobody is around me for long enough.

A lot of drivers don't know the horizontal clearance of the vehicle they drive every single day. That's my theory anyway.

I think it depends on where you live. Where I live, I agree with you, but there are certainly areas of our country where I'd fully expect it to be malicious.