You have my permission to knock them over. The chance of your knocking me over is low as virtually 100% of the time I spend on my bike I'm by myself going back and forth to work.

Not throwing stones and on the face of it, using bluetooth on a bicycle seems a lot safer on a bicycle than holding a phone to your head. However, there is recent research showing that, at least for motor vehicles, using handsfree technology did not reduce the increased risk of mobile phone calls while driving.

Be safe.