I don't know why either. But I would love to know why people worship invisible men up in the sky, pollute the oceans, and killing each other in droves, yet have the audacity to call it religion?
Because people like to think they are smart.
Human nature is to dominate each other. Religions are human institutions created for the purposes of humans.
"Invisible men in the sky" is a phrase used by people who, in their attempts to sound logical and intelligent, illustrate a complete failure to gasp the difference between spiritual belief and artistic expression.
All in all - it boils down to people being self-centered and reluctant to develop their being into the world around them. Instead, they prefer to try and develop the world around their preconceptions of what the world should be. This is the crux of evil - the idea that the world (especially the people in it) should behave according to your will.
This is what leads men and any institutions of their creation (central banks, governments, etc) to the conclusion of conquest and oppression. Quite obviously, I must be saved from the exploitation of my employer that I am too stupid to see; from the ignorant trappings of a church I attend, the hateful speeches of talk shows, and I most certainly must be saved from my paranoid delusions of needing a firearm. You're educated. You know better.
Stalin and Mao both used similar logic to convince people to throw each other in re-education camps (or just prisons where you may as well have been killed).
Don't be surprised when it happens here. We did it to the Natives, and we did it to the Japanese.
It may take a slightly different form - but I assure you that there are a great number of people in this nation who would support the detaining of conservatives and/or libertarians, particularly if it were re-branded in less obvious terms. I don't expect it will happen very soon - since it's difficult to enforce anti-conservatism using a conservative-heavy police and military force... but the fact that there are people who think it would be a good idea should be concerning enough.