I think this is a simplified definition. In most minds and dictionaries a professional is someone who engages in an actual profession, requiring specific education. But we all digress, and I mostly agree with what you're saying. I have a professional day job, by anyone's standards, and I do consider myself a professional SP as well because I conduct myself and my business in a professional manner. Some might find that laughable, but regardless of which job I'm doing, I'm still me & that's my view.
As for negotiating, the way I see it is that whether you view my service as a service or a commodity, in the culture I'm accustomed to, bartering is considered tacky for either service or commodity. I also believe my rates are below what I could easily demand, so when I receive emails or requests for deals and negotiations, I'm instantly peeved. That said, I don't see any need to be rude. My reaction is based on my values and experience, so I keep it to myself. I politely let people know that's not something I'm interested in. That said, when I receive emails and messages that read "bj Rate??!!!" I'm tempted not to reply at all.
I guess the point that many have made is that this particular little world of ours is uncharted ground, so we are all going to carve out our little comfort zone and live in it-- but there's no need to forget manners when asking to open negotiations or when faced with the question. It doesn't all need to be so personal and emotionally-driven. Professional, not professional, take an offer or leave it. We're all just trying to meet each others' various needs & have fun doing it.