When you are acting in good faith and the person/organization on the other end isn't, you aren't having a productive discussion or negotiation, just wasting your own time.
The only sensible approach here would have been to cease all correspondence after their very first email/threat. The nation of Malta would survive just fine without you looking out for them and their online security.
cynical. worst part? best one can do in this situation. can't imagine how I could continue any further interaction with such organization.
Agree - yet, security researchers and our wider community also needs to recognize that vulnerabilities are foreign to most non-technical users.
Cold approach vulnerability reports to non-technical organizations quite frankly scare them. It might be like someone you've never met telling you the door on your back bedroom balcony can be opened with a dummy key, and they know because they tried it.
Such organizations don't kmow what to do. They're scared, thinking maybe someone also took financial information, etc. Internal strife and lots of discussions usually occur with lots of wild specualation (as the norm) before any communication back occurs.
It just isn't the same as what security forward organizations do, so it often becomes as a surprise to engineers when "good deed" seems to be taken as malice.