The freedom to deny others the same freedom?

If it’s all your own work then a license is purely for others to follow. MIT and GPL license can be just as simple as including a textfile of that license in the project.

Ideally one includes a header in each code file to ensure people just looking at that file (without project context) know the license.

Cancer is a bad analogy. It’s more like antibodies against non-free bactetia :)