This doesn't seem any different than the language wars that take place here. In fact, you could cherry pick anecdotes to support hate towards any demographic- age, hometown, music preferences, etc. An MBA proves nothing more than the candidate was interested in pursuing graduate level education.

I'm a solo technical founder. I write code, marketing copy, and proposals. I'm a product manager. And my MBA curriculum covered areas that would be a huge help to product managers.

If you auto-reject CVs with an MBA, you're missing out on a great talent pool. Perhaps you should only give "black marks" to candidates who are clueless about what it takes to manage products. But don't tie that to the MBA.