Right vs. Left : Why All The Hate?

In America, there are hardly any centrist politics at all nowadays; it seems that you're either lumped in as a "liberal" or a "conservative", regardless of whether or not your political ideologies conflict with that of the rest of the community.
America has come a long way since the McCarthy "red-scare" era, but it still has a journey to undertake if leftist ideologies are to take a better hold. I feel that Europe is considerably more evolved than the Americas when it comes to politics, because we do actually have that freedom when it comes to our political ideologies. This is evidenced in France through the strong presence of leftist parties such as the PCF (Parti Communiste Français) and the PS (Parti Socialiste), as well as some of the extreme right parties such as the FN (Front National).
I personally think the liberal and neo-con parties would be united if they formed together to struggle against a common enemy: the far-right racist and neo-Nazi racial separatist parties that seem to be springing up like wildfire across the United States. While freedom of speech is supposedly valued in the United States, these civil liberties are exploited by such personalities as Tom Metzger, a neo-nazi radio host and self confessed racist who used his radio show as a medium for spewing forth his racist agenda, urging like-minded individuals to strike out against the US government. While law enforcement agencies such as the police and the FBI are keeping a close eye on Metzger, they have so far been unable to charge him with breaking the law, as he words his message in such a way that he is not actually breaking the law, and protected by his first amendment rights.
I believe that if the United States government were to pay more attention to people like Metzger, the leftist community and the centre-right politicians would have a common enemy, thus sweeping aside more trivial disputes that they have between each-other. This would be beneficial, as the parties would not be trying to simply win elections, but would work together to create a better society to live in.