What is pseudo-science and when do charges of pseudo-scientific thinking generally arise? These questions are answered by looking at six examples where the charge of pseudo-science has arisen: anti-vaccination and the claims that it causes illnesses, Creationism – the claim that the Bible is literally true –, chiropractic and claims about curing cancer and the like, pre-Darwinian evolution, that is developmental hypotheses before the Origin of Species (1859), Immanuel Velikovsky and his book, Worlds in Collision, and the Gaia hypothesis that the Earth is an organism. It is agreed that there is an objective foundation to charges of pseudo-science and the author’s testimony in a court case in Arkansas in 1981, arguing that Creationism is not genuine science, is used to support this claim. Karl Popper’s criterion of demarcation invoking falsifiability is a key notion here. However, it is argued that charges of pseudo-science occur most frequently when conventional practitioners are under threat. Then claims of pseudo-science are used to attack the non-conventional opposition. The examples are used to support this conclusion.