Someone who is insane has, by definition, lost his ability to blend into society. The author is describing Antisocial Personality Disorder (APD). Colloquially, people with APD are often called sociopaths or psychopaths, but they are never psychotic. Psychosis refers to a loss of contact with normal reality—the person experiences hallucinations and delusions—and is usually involved in cases where the insanity plea is considered.
People with APD can be intelligent and precise, but they know exactly what they’re doing, and that society considers their actions wrong.
Intelligence is a knotty concept, especially since researchers can’t agree on a definition or how it works. A definition that pulls on most of the explanations is the ability to process, store, and retrieve information efficiently; to make unique connections among ideas and events; and to navigate the world in a way that works well. The more "intelligent" one is, the more efficient one's processing ability and the better one is able to navigate the world. (The stereotypical, socially-awkward brainiac navigates extremely well, but with information that is difficult for most people to understand. It can also be difficult to relate to others when they don't understand a lot of what interests you. It's similar to having a hobby others don't share, since it can be hard to try to interest others or explain your hobby to them.)
IQ scores are only relevant in the context of your environment. In other words, you're being compared to everyone else. If you have an IQ of 100, the most common IQ, your IQ is higher than 50% of people's and lower than 50% of people's. (Thus, your IQ is equal to the mean, media, and mode; you have an "average" IQ.)
About 68% of people have an IQ between 85 and 115 (within one standard deviation of the mean); about 95% have an IQ between 70 and 130 (within two standard deviations of the mean). People who have IQs below 70 or above 130 (more than two standard deviations from the mean) are "outliers"—they have unusually high or low IQs.
So what is the IQ score that makes you gifted/genius? Some people will say 130 and above, some 145 and above, and a few will give you a higher number.
Einstein, Benjamin Franklin, Stephen Hawking, and Bill Gates all have or had IQs of about 160. Technically, there are no current tests that can provide an accurate IQ score above 160. In the past, a now-outdated test called the Stanford-Binet could.
That aside, actor James Woods and chess player Bobby Fischer are said to have IQs over 180; Buzan's Book of Mental World Records says the highest IQ guesstimation for an historical figure is 220 Stanford-Binet for Leonardo da Vinci.
