Kathy Griffin has apologized for posting a video of President Trump's severed head after a furious backlash, sparking the Secret Service into an investigation.  The controversial comedian tweeted 'I am sorry. I went too far. I was wrong' after Griffin was seen slowly raising Trump's head during a photoshoot with infamous photographer Tyler Shields.  The Human Rights Campaign (@HRC) honored Kathy Griffin as an "Ally for Equality." Do they support Griffin's threats against the President? pic.twitter.com/snp6y01zUS — Stefan Molyneux (@StefanMolyneux) May 30, 2017 She also posted a video promising to remove the offending image after she was lambasted by all sides of the political spectrum, including Chelsea Clinton. I am sorry. I went too far. I was wrong. pic.twitter.com/LBKvqf9xFB — Kathy Griffin…