It is possible the guy has some sort of mental illness?
I have a cousin with bipolar disorder, when he's stable he's tries to make up for the crazy/weird things he said when manic, only to say it all again next time. When people go hard on him for that, he gets depressed. It's a roller coaster ride! I sympathize with anyone affected by a mental illness.
Sometimes it's hard to take, but you just have to understand they cant help it and in most cases would give anything to be free of it.
...Or he could just be a jerk?