Okay, you deserved to be called pro if most people in the community like you, and you've earned your way up to a Custom Belt(or 7th Dan and up, maybe). But some people, are just naturally good at the game, they are as good as those belt, but are lowly belts themselves. And of course, the devs will also be called pro for several reasons, users in certain clans, if they won the WC, best ranked user, etc. You might not know it, but someone think that YOU are a pro.
So all in all, it really is a matter of opinion.