Earlier quoted context omitted.
The problem is that an open source project you contribute to can become non-free from under you at any point. This pattern is becoming more and more common now.
There are ways to prevent that which in retrospect we should have paid more attention to. For example, (L)GPL with no CLA cannot be changed later.
I think both opinions are fine, if you don't want your contributions to end up in a commercial product, you can't contribute to a project with BSD/MIT license. On the other hand most companies prefer to support projects with a permissive license over projects with copyleft (GPL). For many projects (except the big ones like GNU/Linux) copyleft seems to be more of a burden.