Wrong. They are entitled to the legal presumption of innocence, but not a prejudice of such.
Would you be open to the prosecution's proof that these Marines committed the atrocities alleged? If not, you would be bounced from a civilian jury (and, I presume, a military court martial). I've seen a juror bounced because, among other things, she was (visibly) rooting for the defense.
If a prospective jurer asked by an enquiring attorney for the defense, "Do you think Chaplain X is innocent?" and the prosp. jurer said, "No.", then that jurer is tainted at the outset.