fallacies

---The Straw Man fallacy is committed when a person simply ignores a person's actual position and substitutes a distorted, exaggerated or misrepresented version of that position.

When people are trying to back up their theories, or cut down others, they can use this fallacy. By distorting the position, the antagonist can more easily discredit, or cut down the theory. When in fact, they aren't even attacking the actual position, but instead the distorted view of the position.
http://www.nizkor.org/features/fallacies/straw-man.html
---The Slippery Slope is a fallacy in which a person asserts that some event must inevitably follow from another without any argument for the inevitability of the event in question.

From a seemingly simple statement, people try to "rationally" get from that point to another, more radical point. This can also be used for discrediting theories. For example; If someone believes there is life on other places than earth, they probably believe that they came to earth , and they brought with them all our technology and that they have been controlling us through our technology. A series of steps, where eventually they get out of control.