John Piper and single issue voting

Josh Harris, in an excellent post on Barak Obama and single issue voting, draws our attention to this provocative (and persuasive, in my view) article by John Piper on why he is a single issue voter (and why you are too).

Here's a snippet:
"there are numerous single issues that disqualify a person from public office. For example . . . a person who said that no black people could hold office-on that single issue alone he would be unfit for office. Or a person who said that rape is only a misdemeanor-that single issue would end his political career. These examples could go on and on. Everybody knows a single issue that for them would disqualify a candidate for office. . . . I believe that the endorsement of the right to kill unborn children disqualifies a person from any position of public office. It's simply the same as saying that the endorsement of racism, fraud, or bribery would disqualify him-except that child-killing is more serious than those."