So is it against the law to give the plan of salvation to them?
And do we have to provide Korans to them to fuel their hate of us?
No, I wouldn't go that far. There is no law saying that we must give any prisoner any kind of book nor that we cannot proselytize to them irregardless of what certain groups (such as the ACLU) say.
Witnessing to these people and trying to force them to denounce their beliefs are two different things.