Everyone has the right to basic human rights. If an individual doesnt respect them, then that is no licence to lower our own standards as human beings. Where would that put society? Look at societies now who operate on an "eye for an eye" basis.
Where would you rather be - Gaza/Iraq/Afghanistan, or here?
There are many things that constitute basic human rights, and yet, if someone commits an act that is so heinous, then society is entitled to impose punitive action on them for the following reasons: to rehabilitate, to restrict, and/or protect society.
The people you have spoken to will have undoubtedly have had an element of bravado in their description of prison. It certainly isnt a bed of roses. Yes, they get their 3 meals a day - part of their basic human rights. Most prisons have 20 hour lock up - often in 6ft x 4ft cells. If you think this is comfortable then you are mistaken.
Prisoners do get benefits for good behaviour in prison, and, I think that this is a good thing both for their self esteem, to assist in the rehabilitation, or, for the prison to function well and prevent further bad behaviours.
It's not perfect in all prisons by any means, but the day we start putting a value on someones life and their ability to live it out, is the day that we devalue the lives of those lost in the hands of a murderer.