You might be misunderstanding the structure of the Shadow market. The devs do not "allow" anything on there. They write code. They release the code, and what we buy and sell there is what we buy and sell, they can't control any of it.
I'd add that the way a decentralized app works is that it's owned by the people. So you can't really shut it down unless you control the coin supply which is tied up in nodes at the moment. Roughly 45% or more staking and hardly any supply in the open market without raising the price to $100 or more.
Very expensive overthrow scenario.