Also, people in Guantanamo haven't been "disappeared". They're being detained indefinitely, which is a problem, but we know where they are, and they have access to courts and lawyers (albeit hard-won access).
The "disappeared" in Central and South America were more often than not murdered.
There's also, it must be noted, a fairly enormous difference between "detaining foreigners captured in an active combat theater because the State earnestly believes them to be an immediate, violent threat to Americans" and what the US government has been doing with the detention center at Guantanamo Bay, in which the government has detained many people who it never had any reasonable cause to believe were an "immediate, violent threat to Americans" and many of the prisoners were not captured in an active combat theater.
Just because you have a drum you want to beat doesn't make it sensible to keep beating it when its not relevant.