Context:
Permissive licenses (commonly referred to as "cuck licenses") like the MIT license allow others to modify your software and release it under an unfree license. Copyleft licenses (like the Gnu General Public License) mandate that all derivative works remain free.
Andrew Tanenbaum developed MINIX, a modular operating system kernel. Intel went ahead and used it to build Management Engine, arguably one of the most widespread and invasive pieces of malware in the world, without even as much as telling him. There's nothing Tanenbaum could do, since the MIT license allows this.
Erik Andersen is one of the developers of Busybox, a minimal implementation of that's suited for embedded systems. Many companies tried to steal his code and distribute it with their unfree products, but since it's protected under the GPL, Busybox developers were able to sue them and gain some money in the process.
Interestingly enough, Tanenbaum doesn't seem to mind what intel did. But there are some examples out there of people regretting releasing their work under a permissive license.
Wait, people give other people the right to make proprietary variants of released source code and then are surprised when they exercise that right?
No, other licenses don't protect against not understanding which rights are granted. The GPL, for example, allows to make proprietary web services using GPL code and to never release any modifications to that code. Many people were very surprised many years ago that some web-based messenger could use Pidgin's libpurple to connect to ICQ etc. without ever giving anything back.
It's more like being angry when people try to abuse charities and get money when they don't need it. Like growing an apple tree in your yard and telling people they're free then being upset when someone comes and takes all of them. Or a better example, being angry about people taking all the candy from a Halloween bowl.
That's not what I meant, I meant protect against people taking advantage of your code in a way most people would view as wrong. (Just because something isegal doesn't mean people believe it is right.)
Also, that's why I use AGPL.