The U.S. is a nation of laws.  We have authorized law enforcement officers to, as the name implies, enforce those laws.  We have a judicial system to, as the name implies, "judge" the guilt or innocence of those accused of crimes.  Those systems are now functioning to adjudicate the allegations filed against the Bundys and their militia friends.  

It's not the role of citizens to, on their own, intercede in this process.  Your suggestion that anyone who disapproved of the Bundys' actions should have travelled to the Malheur Reserve and confronted them about it is ludricrous.  

Law enforcement officers did meet with Ammon Bundy and Finicum in an effort to convince them to surrender peacefully.  The Bundys chose not to.  Only when they were stopped on the highway and "forced" to surrender did they do so.  At that time Finicum still refused to surrender, refused to follow the orders from law enforcement officers, shouted "you're going to have to shoot me" and reach for his pistol...