This controversy is being drummed up disingenuously by Democrats and their allies in the media. Trump wasn't calling for Cheney to be shot, he was making a point so that even the mainstream media can understand it. He was explaining how warmongers often don't even serve in the armed forces and often don't face consequences for sending other people's children to fight. Democrats and the media should feel outrage toward the war hawks rather than Trump.
Sadly, this is the type of rhetoric America has gotten numb to from Trump. In addition to not being the first time he has called for one of his opponents to face a violent attack, he's also continually lashed out at female critics while aligning himself with a number of misogynistic figures. This is un-American and should disqualify Trump from being the next president.