An "activist" is a vigorous advocate for a cause. Famous activists have included Martin Luther King, Mohandas Gandhi, Lech Walesa, and Leo Tolstoy.
Scott Roeder is not an activist. He is a "murderer," or most accurately, an "assassin". Please amend your headlines accordingly.
I recognize that the appearance of objectivity (as opposed to actual objectivity) is important to journalists, but please, show a little perspective.
Next week, we'll discuss the word "militant".