I mean this wasn't negging as I've heard it described. Negging is supposed to be a very subtle remark or action that suggests "you're not as attractive as all these fawners say you are" that you say to the hottest girl in the bar. This "technique" for lack of a better term has been around for ages and used to just be called "playing it cool". In any case, if you're already texting, the time for "negging" is past (although playful teasing in the same vein can continue).

But this here was just the insults of an insecure man who's being shot down and is trying in the most insane and counterproductive way possible to rescue his ego.

The real mistake here was asking the birth control question via text message to a girl whom (I presume) he has never had sex with. That was insecurity talking: this is a man who does not trust himself to take the necessary precautions in the moment. You can easily ask that question when the clothes are coming off, and frankly you need to be taking your own precautions anyway (i.e. use a condom that you brought) until you have actually grown to trust the girl.

OP dodged a bullet here. Dude has a lot of growing up to do.