There are two problems in your argument.

1. Mainstream US economics and politics is dominated by varying degrees of Keynesianism or Neo-Keynesiansm. Even the Republican mainstream (not talking about Ron Paul / libertarians, I'm talking about Mitt Romney).

2. Republicans are very supportive of measures that increase national security. If Bitcoin ever becomes widely used by terrorist organizations to shuttle money or other criminal organizations (as it appears to be used on a smaller scale already), then some Republicans would turn against it.

Combine this with the fact that the White House and Senate are controlled by Democrats, and you could very well see government action against Bitcoin.