i'm pretty sure you don't have first amendment rights in jail. losing access to instagram would seem like one of the consequences for robbing or killing
We're just gonna assume that the system is working perfectly and only guilty people are being punished.
To lock a mf up in the first place is the ultimate taking of rights. Freedom. The principle that America is based on. Your very ability to go where you want is taken away.
Any other rights that are lost are a small percent loss on top being put into a cage.
If you can legally put person in a cage, you can do anything short of physically harming them. And even then, plenty of inmates get physically abused and even killed. By the guards and by the other inmates (you'd imagine that the system would protect the inmates from being beaten, raped, or killed by other inmates).
In summary, stopping inmates from communicating is only slightly worse than the basic concept of prison. If we allow prison itself, then this detail is miniscule.
But. We know that the system is not perfect and plenty of people who don't deserve physical and mental abuse get subjected to it.