There are understandable differences of opinion between the American and Israel leaders on the issue of Islamist terrorism. It is wholly appropriate and desirable that they should be heard in the U.S. Congress. It is therefore painful that some honorable Democratic members of Congress should be so misguided as to declare that they will not attend the Israeli leader’s address. John Lewis (Georgia), a hero of the civil rights movement, G.K. Butterfield (North Carolina), chairman of the Congressional Black Caucus, and Eric Blumenauer (Oregon) are among those who are engaging in what is tantamount to a boycott of Israel. According...