Philip Plait debunks weird, pseudoscientific claims at his excellent webiste badastronomy.com. Here’s his take on what it’s like to stand up for science:
Have you ever gone to a carnival, or a fair of some kind, and played the game “Whack-a-Mole”? It’s a table with holes in it, and little mechanical rodents pop their heads out for about a half a second. You have to hit them with a mallet. If you wait too long, they duck back under. But every time you hit one, one or two pop up again. No matter how many you whack, there are always more.
Pseudoscientists are like those moles. You can whack one down, but then another springs up…
He does an excellent job of it. For a taste, read his debunking of the claims that the Apollo moon landings were faked.