Whiteboard markers

An unpopular teacher walks into the classroom at the start of the lesson to find, written in large letters on the whiteboard, the phrase

With facts used clearly marked, try to uncover better instances of heresy.

Assuming that it was left over from the previous lesson, she will reach for the board rubber and begin to erase the quote... only to discover that certain "choice" letters have been written in permanent marker, leaving

     f     u    c          k      y  o u       b      i  t  c      h     .

Cue hilarity.