I think there are already many defenses at the initial, Asking, point. And none is intrusive, only some alerts about the title, content and tags. As I understand it, registration is only required in this Meta and Stack Overflow. And that's about it, nothing more, go and Ask.
IMO any intrusive resistance is futile because the input field for the Question title already has:
That doesn't prevent, at all, questions about Career Advice or more exotic stuff.
I've answered a similar Q at Meta Ask Ubuntu. Its main site has the following in the input field:
What's your Ubuntu question? Be specific.
Ubuntu has zero relation with Chemistry, that didn't prevent someone asking about Atoms & elements...
The cherry on the cake goes to someone asking a Microsoft question at Ask Different (Apple) that kindly reminds us on the very first field:
What's your Apple hardware or software question?
We are doomed to receive blind asking folks from all over at increasingly alarming rates.
The force is in self-moderation. I think the problem lies on the Close Vote Queue and that's being tackled at this very moment.