No. There are many experts whose letters on their areas of expertise refuting others whom they perceive to be in error don't get published. All you generally see is what is published, not that which isn't. Your awareness of THIS letter does not mean that it is an exception.
If Ann Coulter herself wrote in to correct a column of grave factual error, then that letter is likely given more consideration. The WSJ not publishing a letter is their prerogative, your--or Mr. Evans--personal support of Ms. Coulter notwithstanding. And non-publication is not that unusual, your opinion of Mr. Evans notwithstanding.
M. Stanton Evans is *the* expert in this particular area. Unless the WSJ is totally asleep at the wheel, not running this letter was a deliberate act, the ramifications of which should be carefully considered by conservatives.