"So, if the lake is like this," (Gestures a circle with her hands) "the ocean is like this?" (Gestures a bigger circle)Often, woos seem to have no grasp of how big or how old the universe is. Science is often the art of putting numbers on things so that we can understand them.
"Not even close."
"Like this?" (Gestures with her whole arm span)
"No, it's like," (Looks up) "...it's like the sky."
One of the categories particularly guilty of this is the Creationist. They like to pull rather unlikely probabilities out of their back pocket using bad math, but often when they try to cite how unlikely many things are, they forget to account for the size of the universe. Many like to point out how unlikely it was that this exact ball of rock we live on would have been habitable for life, but they forget that the universe is an enormous place. If it didn't happen for Earth, there's no shortage of other planets it could have happened to. If enough people play the lottery, you can bet someone is going to win, eventually. And, thanks to the anthropic principle, the losers aren't around to complain.
Other woos, such as those who believe in psychic powers and other magical means of divination, underestimate the power of coincidence when combined with confirmation bias. For example, many people have worries about their friends manifest as dreams about them being in danger. Usually we write these off appropriately when they don't come true. Woos of this sort usually do that, except if the dream coincidentally comes true. There are enough superstitious people out there that it happens, get spread by word of mouth, and suddenly a normal form of anxiety becomes a vision of things to come. Sometimes it can take over a person's life.
This is a difficult problem to overcome. A decent grasp of mathematics helped me realize where I had be going wrong in my young woo days with just the explanation, though. About all I can think to do right now is encourage better math education and, when in an argument, push for quantitative measurements.