Generally speaking, the output of a program running on input I provide is not a derivative work of the program. It might contain pieces belonging to others (e.g. clipart, canned boilerplate code) that are subject to their own licensing, but the overall work and the pieces derived from my input belong to me.
Why, then, do you suppose that providing a useful tool gives you any moral authority to restrict what other people do with their own property? As @leftaroundabout remarked, that's the opposite of freedom, and I myself find it borderline offensive. It's also specifically contrary to the FSF's view on free software. As you observe, the GPL does not impose a limitation such as you seek, and that's intentional.
If you nevertheless want to pursue what you describe, then the first thing to do is immediately stop distributing your software under the GPL. Any copies distributed under that license are free of the constraint you want, including any that have already been distributed. The GPL does not permit you to make post hoc license changes to copies you've already distributed.
You'll then need to devise your own license that places the restriction you want on licensees, and henceforth distribute the software only under that license. It will be an open question whether the terms pertaining to licensing of the program output would stand up in court if you ever try to enforce them, or what remedy a court would be willing to grant if you prevail in such an effort. Nevertheless, the mere presence of those terms might be enough to mostly achieve your aim.
Personally, if I were considering using software licensed as you describe, the license terms would be a deal killer. I'd sooner accept restrictions on redistributing the program, and maybe even closed source, than I'd accept restrictions on what I can do with the output.