Not to be picky Spooky, but I'm not sure you can rely purely on one source for definitive definitions for argument purposes.
Language is a living thing (coming out of living things...). Meaning of words change over time and for "professional" it was definitely the case. In the old days someone who made their living with a particular activity was called a "professional" of that particular activity. This in turn meant in most cases he was very or sufficiently good at that activity, otherwise he wouldn't be able to make money out of it. So over time a "professional" was called anyone who was good at a particular activity, regardless of whether he makes money out of it or not.
For example, I could have posted what wiki says "professional" means and it would have stated the opposite of what you have here.
No it does not

. From wikipedia:
Less technically, it may also refer to a person having impressive competence in a particular activity.
Although wikipedia actually references to askoxford for this definition.
I'm just suggesting that using a single citation as the endall of debate is usually not sufficient to close arguments.
I don't want to say that either. But it seems for the OP it was clear that "professional" has only one true meaning and he apparently did not understand, why people call skilled players "professionals".