Helmets are mandatory in all major cycle competitions - so I'm not sure this reveals a preference among professional cyclists, so much as a preference among competition administrators.
The question is actually more interesting with public health. I have seen several studies that showed that mandatory cycling helmets decrease life expectancy. That's because less people will ride a bike if they have to wear a helmet and the benefits of cycling outweigh the dangers of not wearing the helmet. That doesn't mean it isn't good to wear one anyway if out cycling.
>Also in terms of common sense consider that all professional cyclists wear helmets when they're competing.
Mentioning professional cycling does not help your argument. The riders organisations were fighting strongly against mandatory helmets, and professional cycling was very late with requiring helmets they came many years after they were mandatory for amateur races. There is also the observation that professional cycling has become riskier, although I would not necessarily link that to cyclist wearing helmets, it would be worth investigating though.
I'm getting real sick of the, "your feelings" talk. You used to get socked in the eye for talking to people that way in public. There's a better way of expressing your point than speaking to proverbial others as though they're children. It's enormously toxic.