@icedquinn It's less about GPL's validity and more that you have to launch and sustain a copyright lawsuit if someone violates your license - those things doesn't automatically kick in the way how, for example, the criminal code works, in my understanding - which is rather unpalatable to a lot of people
(Though if you're able and willing to do it, more power to you!)
In general I want my software to be libre too, it's just I'm not entirely convinced that doing it through the courts - and in particular, through the copyright system - would be a very effective way to it