If the prison doesn't want tourists; why let them in?
I've never been to Bolivia, but I have read the Marching Powder book, and I found it fascinating.
I don't agree that this is really the fault of the tourists though. What other working prison in the world allows tourists to visit freely?!
In small numbers I don't see the problem - it's a fascinating experience for the tourists, and a money earner for the guides and guards.
It's a prison - and it's the prison authorities that are allowing the tourists to enter. It would be easy to stop tourists getting in - if the prison wanted to stop it.