According to a press release posted on his website:
http://www.manchin.senate.gov/public/index.cfm/press-releases?ID=237cbd66-6a26-4870-9bcb-20177ae902b0
"Today, U.S. Senator Joe Manchin (D-W.Va.) sent a letter to federal regulators seeking a ban on Bitcoin, the virtual currency that is unregulated and unstable, and has been used in illicit activity, including drug trafficking and money laundering."
So apparently bitcoin is very dangerous and we should all be terrified of it, because:
1. It is unregulated. Because without government regulation, how would money work?
2. It can be used to fund illicit activities. Unlike cash, for example.
3. It is highly unstable. Look how much its value has increased over the past year alone! Runaway deflation, oh no!
4. It is "disruptive to our economy". The economy was running nicely until bitcoin came along, and it's something completely different that didn't exist before, so it must be stopped.
Anyway it's predictably idiotic fear-mongering. The senator probably barely understands what bitcoin even is but the bankers who fund him don't like it. Toward the end is this gem:
"The clear ends of Bitcoin for either transacting in illegal goods and services or speculative gambling make me weary of its use." Quit clinking around all those noisy bitcoins, the senator needs his sleep!