Given that he announced it as a joke when saying the word,
He didn't announce it as a joke. He said the whole thing (including the dramatic pause and punchline) in a very serious, premeditated way, and didn't laugh or smile after he said it, even after the congregation laughed louder than I've ever heard them laugh at anything. He normally interjects more spontaneous one-liners, such as....
"that first service is a tough crowd but you guys are ok", or
"this side of the room didn't get that (points to left), but I'm glad this side is with me." (points to right). Normally there are at most a few chuckles.
I think most people laughed cause they just like him, and perhaps there was some shock value to it, like "can you believe he actually said that? haha").
It's the smallest church I've ever been a part of and I think pastors of smaller churches can get away with more without seeing a drop off in attendance compared to a megachurch where most people there have never even stood within 3 feet of the pastor and will leave over the drop of a hat and not come back. A drawback is that smaller churches typically lack any growth, but that's fine with people who like an 'everybody knows everybody' atmosphere and just as soon not have it grow. I can maybe see a visitor or newcomer not like the pastor now and say 'this church is not for me,' but I'd be very surprised if anyone who has been around awhile will leave just over the pastor's sometimes zaniness, or as he likes to say, 'the cheese slid off the cracker.' It's a very laid back, casual, informal church. It's been around long enough to see that it's as big as it's going to get.
It seems like the more conventional, institutional churches are the ones that grow cause they're more cognizant of how every little thing might be perceived by visitors, and they work harder to keep up an image that won't offend anyone.
Another megachurch in the area has huge growth, planting new locations every year. Again, I can't imagine the pastor at their main location wasting even a few seconds in the pulpit to share and acknowledge the cynical communication of an anonymous person whose comments they clearly despise.