It is often good advice to be skeptical of statements by politicians when they seem to contradict themselves, although in this case Bibi's words did not.
But is it wise to be skeptical when the dictator of a nation building nuclear weapons and ICBM's say "Death to America"?
In an address in Tehran on March 21, Iran's Supreme Leader Ali Khamenei responded to the crowds' chants of "Death to America" by saying: "Death to America, of course, because America is the principal element behind this pressure [i.e., the economic sanctions]." Khamenei said that Obama had said "some dishonest things" in his Nowruz address and that the American goal was "to turn the [Iranian] people against the system." The address was broadcast on the Iranian news channel IRINN.It is not even worth mentioning when Khamenei's top aide says "We shall not rest until we raise the flag of Islam over the White House.”
The White House is skeptical of a democratic ally's peaceful intentions but equally skeptical of an avowed enemy's vow to destroy America.
In other words, the White House only believes that "words matter" when the skepticism fits their agenda. In this case, their viewpoint is that peaceful statements from Israel must be insulted and warmongering from Iran must be coddled.
(Bibi explained his words, and why they weren't contradictory, on NPR.)