Metropolitan police say an advocate for the city’s homeless was fatally stabbed by a man he had tried to help.Samuel Fancher, 45, was charged Wednesday with murder in relation to the Nov. 22 death of Gregory Kemp, Lt. Jeff Duhamell said.Fancher was arrested in December on a parole violation for a robbery conviction and will be served with an arrest warrant at a Department of Correction facility, Duhamell said. Kemp, a faith-based counselor for the homeless, was found dead inside his Westside home in the 2200 block of North Groff Avenue about 4 p.m. on Nov. 22. Kemp had worked with Fancher, who police said was homeless when he was arrested on Dec. 4.