This is ruining the game play for blue- brown belts, Its tiring that all these black belts are in Semi pro servers just to "Harvest" on lower levels, Please, Remove this feature, Its really annoying at times.
Some black belts are just as good (or bad) as their lower belt counter parts. And as Zen said, it's possible to just make an Alt and join those lobbies.
Doubt anything would be done because there's such a wide variety of skill levels in black belts alone so you can't really do it because of a minority that's better than some lower belts and might be taking advantage of that fact.
But if they're truly farming then screen-shot or video them doing so. Otherwise nothing will happen to them.