Being a "professional" sailor (getting paid by somebody or having a sponsor or working in a sailing-related business) does not somehow make someone a better sailor than an "amateur" sailor, any more than a rich sailor is a better sailor than a poor sailor. You usually don't become a good sailor just by virtue of being "professional." It's the other way around, usually you become a professional sailor because you are a good sailor. The best sailor will win the races, whether "professional" or not. I think it is just a psychologically intimidating label.

Saying you don't want to race against "professionals" is saying you don't want to race against the best. Racing against the best is what raises the bar for all of us and makes us better sailors. If you are a good enough salesman to get sponsorship for yourself, you, too, could be a "professional." Personally, I think all racing sailors should use their sails as billboards and get sponsors, whether large or small. But it won't make you a better sailor. You have to do that for yourself, and the best way to do that is by racing against the best.