Why would you think he's kidding? I don't see a veiled attack: I see desperation. He (and others in this thread) believe that you are putting yourself into greater risk by calling 911 than by solving the situation any other way you can.
I don't share their opinion, but I would think deeply before dismissing the sincerely expressed belief of those who feel the emergency response system in the US so broken that you are better of trying to make your own way to medical care rather than taking a chance on calling 911.