It’s Not the End of the World
First, forget about the guy leading this group, and think about the folks who followed him. They, without any doubt, were very sincere in their belief that the interpretation he put forth was correct. They followed because they believed. Can you ridicule them for that? After all, we follow our beliefs, and to an unbeliever, what we believe is every bit as ridiculous as what these folks believed. How can we poke fun at them and then get offended when atheists make fun of us?
We can't. They believed sincerely, so much so that many acted on that faith, refusing to hedge their bets. They got rid of their property, their savings, anything that could hold them back from meeting God. We're called to do the same, you and I.
How many of us have a faith strong enough to let go of everything, and depend solely on God?
I don't, and so I have admiration for those people who, even though they were mistaken, went all the way for their belief. They literally put their money where their heart is, and while they may seem foolish to most of us, I admire their courage to act on their faith, to step out of the boat onto the storm tossed waters, and believe that God will sustain them. My prayer is that they will be sustained through this trial, that they understand that it wasn't their faith that was wrong, but the teaching they followed. I pray that their faith in God withstands the pain this false teaching has brought them.
My guess is that for most of them, it will. They understand that man is fallible, and makes mistakes. We can be misled, blinded by our own pride, our intellect, or by influences of the world. While we make mistakes, some admittedly bigger and more public than others, we know that those mistakes do not reflect back on our faith, but only on our own shortcomings, our own misunderstandings.
As for the guy who led them, I don't know if he was simply wrong, or if there was more going on, but either way, his burden is heavy. The Bible tells us what happens to false prophets, both in this life and at judgment, and it isn't pretty. Millstones and oceans are involved. In short, he will get what's coming to him; I don't have to get involved in it. God will sit in judgment on him; I don't have to.
In short, these folks deserve sympathy, not scorn; empathy, not ridicule; love, not judgment, our admiration, not condemnation. They stepped out in faith, doing what we profess to do, but doing it better.