Kohler tub spouts attach to the pipe nipple, or the short length of pipe that protrudes from the bathroom wall, using threads. This means you must turn the spout clockwise to thread it onto the pipe nipple and counterclockwise to unthread the spout. Using a strap wrench presents the least amount of risk that you will damage the spout's finish, but if you do not have one you may use a towel and pipe wrench.
Slide a strap wrench over the end of your Kohler tub spout. Slide the wrench's strap to about halfway up the spout and then tighten the strap by pulling on the loose end so it fits snugly on the spout. Turn the spout with the strap wrench counterclockwise to unthread it from the pipe nipple.
Wrap a thick hand towel around the tub's spout if you do not have a strap wrench. Clamp a pipe wrench onto the spout over the towel, and then turn the spout counterclockwise to remove it from the pipe nipple.
Clamp the pipe wrench to the pipe nipple if you see signs of corrosion on the nipple, such as rust. Turn the nipple counterclockwise with the wrench, unthreading it from the connection in the wall.
Wrap plumber's tape clockwise around the threads on both ends of the pipe nipple, as well as the threads on the back of the tub's spout.