Well, depending on how “hostile” the environment is, you may have a lawsuit, especially since it doesn’t look like your boss is going to do much about it.
Meanwhile, I would do things that would make CtAC think he is losing his mind. Slightly rearrange his desk or his computer settings (wearing gloves of course, this guy sounds icky.) Make appointments for him that get him out of the building for hours on end. Etc. I’m sure you and your fellow sufferees can come up with more!
The last time he was messed with, someone hid his electric pencil sharpener. He spent three hours running around the building looking for it. Someone else posted reward signs on all the bulletin boards.