The best example I could point to would be BSD. Unlike Linux, the BSD kernel was BSD (essentially MIT) -licensed. This allowed Apple to take their code and build OSX and a multi-billion dollar company on top of it, giving sweet fuck all back the community they stole from.

That's the moral argument: it enables thievery.

The technical argument is one of practicality. MIT-licensed projects often lead to proprietary projects (see: Apple, Android, Chrome, etc) that use up all the oxygen in an ecosystem and allow one company to dominate where once we had the latitude to use better alternatives.

• Step 1 is replacing coreutils with uutils.
• Step 2 is Canonical, Google, or someone else stealing uutils to build a proprietary "fuutils" that boasts better speeds, features, or interoperation with $PROPRIETARY_PRODUCT, or maybe even a new proprietary kernel.
• Step 3 is where inevitably uutils is abandoned and coreutils hasn't been updated in 10 years. Welcome to 1978, we're back to using UNIX.

The GPL is the tool that got us here, and it makes these exploitative techbros furious that they can't just steal our shit for their personal profit. We gain nothing by helping them, but stand to lose a great deal.