Don't worry about that. They hate you because you exist.

Be big, both in attitude and appearance. Don't hide on the on the road, be out there where they can see you. Don't shy away from cars (unless absolutely needed to avoid a hit), be bright colored and alert. When it is your right of way, take it and be seen taking your right of way. Use hand signals. Look at people, when you go, go aggessively. Be predictable, don't wobble around, make your moves smooth and consistent.
I have used a flag mounted sideway out to the left of my handlebars in the past. It definately works to eliminate close passes, but limits your maneurverability. My flag stuck out to the left about 32" and was armed with a shiny metal point and a flag. While using it I never experienced a close pass.