If it was me and I had to cancel due to a medical procedure causing me more recovery time than anticipated - I would be very apologetic (which apparently he was).
If someone responded: "You should have told me the night before" - I would have apologised again and explained that while I thought it would be much better the next day, when I woke up in the morning it wasn't. Therefore I tried to postpone with as much notice as possible until the pain and swelling improve.
If that person then said "This is a literal joke and I've been let down a lot before" I would start to get cross. I would think "I'm in pain, I've given you notice, I've apologised and now you're scolding me and I am somehow being blamed not only for this situation but also for previous people letting you down!" I would be bloody angry.
If I then got a message saying "I'll take your word for it" - I would think "Oh how very gracious of you!" And I don't think I would want to talk to you much at all after that. I doubt I would reschedule to be honest.
Yes he could be a massive arse, love-bomber, time-waster, flakey or whatever.
Or he could just be pissed off because he's in pain through no fault of his own and received no sympathy whatsoever. It took you until today to reassure him it was not his fault but at the time you just made him feel even worse about things.
I mean the conversation could have gone like this:
"I'm really sorry I have to postpone tonight - I thought my mouth/face would be better today but I'm still in a lot of pain and very swollen. If I came out tonight I wouldn't be much fun and it's such a shame as I was really looking forward to meeting up. Sorry again."
"Ouch, sorry to hear that, dental stuff can be really painful. I totally understand. No problem at all. Rest up and fingers crossed that the painkillers/antibiotics kick in soon. Let me know when you're feeling better and we can reschedule."