Are you going to reuse it? If so you won't want to damage it, but if you are using a new one like a chrome one, vise grips can be used to turn it back and forth to loosen it. The tube is just a press fit into the hole.

I had one that was really stuck and had to slip a bolt that was a tight fit into the tube, then clamped the vise grips on that portion where I could really clamp it tightly'

Normally, if you put the vise grips (ones with the rounded jaws) around the bottom as close to the place where it enters the block, you can spin it loose and it will start working it's way out. I have also clamped vise grips on and tapped upward on them with a small hammer to dislodge the tube.

Don