I don't think they should be assisted in devouring freely-accessible data in their endeavor

How is this assisting them, though? I see it as two different options:

1. They use the open-source code without giving anything back; or
2. They use the open-source code and help improve the project by reporting security issues.

In any case, a fundamental feature of both free and open-source software is that anyone can use it, regardless of if you like them or agree with them or not, without discrimination. You could instead use a license that forbids AI training, but then your code would no longer be free or open-source.