Actually Obama has not been silent on this issue...
Obama tells Morsi violence in Egypt 'unacceptable'
"The White House says President Barack Obama has called Egyptian President Mohammed Morsi to express "deep concern" about the deaths and injuries of protesters in Egypt.
A White House statement says the president told Morsi that he and other political leaders in Egypt must make clear to their supporters that violence is unacceptable.
The statement Thursday night said that Obama welcomed Morsi's call for a dialogue with opposition leaders in Egypt but stressed that such a dialogue should occur without preconditions. "