Here's a few reasons:
1. It destroys the individual and promotes the collective
2. Government and the state become more important than the individual
3. I don't believe in stealing one man's hard earned money and giving it to some one else.
4. I believe that the least amount of government is the best form of government
5. It goes against everything written in the Constitution, this country was founded so that people could take risks on their own, without government intrusion, keep their wealth and do with it as they see fit. Not have a gov't agent decide what to do with it.
6. Socialism creates an unhealthy dependence on government. People become lazy and apathetic, knowing that the gov't will always bail them out with some one else's money.
7. Socialism is not sustainable, just look at the countries is Europe who can't pay their entitlements, it is simple math.
Basically, the by-product of Socialism is an ever-increasing and intrusive government which is something I do not believe in. People need to be left alone, let them make their own mistakes, let people live their lives how they choose. I don't need Michelle Obama telling me what to eat, or the EPA telling me what kind of light bulb to use, etc. These are all a result of socialist/collective policies that all sound good, but in the end do more damage the good.