I started riding again in 1990 and rarely have noticed any sort of negative response from motorists. Certainly, I have never been attacked or had anything thrown at me that I noticed. Someone shot a paintball at a group of us in a rural area once, but it wasn't from a vehicle. We thought my leg was bleeding until we figured out what it was. I do try to avoid high density traffic areas and to be predictable and signal where appropriate. I suspect a lot of situations that are taken as threats or rudeness may be simply unconscious cagers. There do seem to be a lot of nut jobs behind the wheel though.