You're right, saying "fuck off" probably wouldn't have helped. I'm unaware of how okcupid's messaging works and working on the assumption that she received the messages whilst online. If so, I feel an early polite but firm rejection would help to prevent the situation from escalating. Failing that, it's common courtesy. This all changes, naturally, if she was offline when all the messages were sent. In which case there was no point in replying.

For me, the 'sad cringe' here was him vocalising an inner monologue of despair a lot of single guys have gone through when being completely ignored on dating platforms. Obviously he should have sent his opening messages and moved on if he didn't get a reply. Part of the problem of being ignored is you don't know where you stand, you've not been rejected yet so you might still have a chance. He clearly doesn't have the introspection to see that the reason he didn't get a response is his little self deprecating monologue doesn't portray any attractive qualities.

I don't see this guy as a threat or 'psychotic', he just seems desperate for affection and is frustrated by being ignored, but I'm no expert. I'd like to think he slept on it, woke up feeling stupid and grew as an individual and went on to find a girlfriend with online dating.