To me it's a "serious security vulnerability" only in the sense that if they were that lackadaisical with their password storage, where else have they made poor decisions with regards to security?

I think you'll agree that security is not a single thing you do, but a series of things that makes getting at sensitive data more difficult. To store all passwords as plaintext (including passwords for administrators, I would assume) surely must be considered a serious oversight at the least.

I feel as though maybe we're missing some nuance in your position on this.