With the media in full frenzy during the past three days over the public feud between the Pakistan-born Khizr Khan, who last week told the story of his son, a Muslim US army captain who received a Bronze Star and a Purple Heart after being killed in Iraq in 2004, and Donald Trump, earlier this morning the Republican presidential candidate refused to back down, defending his criticism of the parents by complaining on Twitter that the father “viciously attacked” him in his speech at the Democratic National Convention.