That's not true. According to the FBI the two groups responsible for the vast majority of terrorist crimes in this country is the FAR RIGHT And Islamic extremists. 
From the NYTimes: The frequency of far-right attacks is particularly significant in the United States, where white supremacist, anti-government and neo-Nazi extremists have been responsible for 73 percent of deadly terrorist attacks since Sept. 11, 2001, according to the Government Accountability Office. Also notable is that in many cases, Muslims have become the target of violence.
Also, blaming the left for the terrorism that we're seeing from the far right is very similar to what Hitler used to do. Hitler blamed the 1933 Reichstag fire on communists. He blamed the Jewish people for everything bad that ever happened and as for his brown shirts? It wasn't THEIR fault they beat the guy to death. Someone egged them on. smh.  
The right needs to take responsibility, stop this from happening and quit passing the buck. 
My $.02