"If someone wants to use a skill they possess to create a useful tool that makes someone's life easier and charge for it, it's their right."

Sorry, 'hold up', you're just a bit off-base here. The word you're looking for isn't "right", it's "privilege", and the administrator of any venue has the overriding privilege of denying you that privilege.

I'll illustrate. (Dear FBI agents reading: I promise that I do not have any intent or desire to actually do the following.) Under your philosophy, if I have the skill of being able to aim and fire a gun, I am well within my rights to walk into the Post Office and tell the people waiting in line that I'll murder the people ahead of them in line if they pay me for it. I am using a skill that I possess (shooting guns) to provide a useful tool (a method of eliminating people ahead of other people in line) that makes someone's life easier (shortening the post office line), and I'm charging for it.

This is clearly absurd. The United States government reserves the privilege of putting me in jail for a very long time if I try that stunt.

Likewise, Blizzard controls the game and the interface. They reserve the right to ban you and your add-on if you break their rules.

It's too bad that you don't like it very much, but that is the way it works.