it is not fair to ban a player for a vanilla gameplay mechanic. The only problem with spawners is the technical side: which is the creation of tile entities that will cause server lag.
The reason behind the spawner being removed is simple. Zero tolerance on lag creating mechanics, which are vital for a survival server. Banning/jailing players will not help us reduce lag. Opening a spawner to the public will only make this worse and not a smart idea.
Removing a spawner when afk'ing near it is the only reasonable way we could allow mob grinders etc.