All the ex-Confederates were dodgy after the war, even Robert E Lee. You can take a lot of what they said two ways or even more! They didn't know whether they were going to be tried, have to leave the country, what Johnson would do or what the radical Republicans in Congress would do. There was the chaos of the war and the huge changes in Southern society with emancipation. There were those who sought revenge on both sides. And, they didn't know what would happen in the wake of Lincoln's death. Forrest wasn't the only former general to lead an insurrectionary clandestine group, either.
If Forrest was enigmatic or ambiguous about things he said, he sure had good reason for it!
We should remember Radical Reconstruction had just ended when Forrest died in 1877. No former high-ranking Confederate felt completely safe during these years – a wise ex Confederate watched his mouth and said and wrote only what the Feds wanted to him to say or write.
I've got no respect for any young man who won't join the colors
Nathan Bedford Forrest