It's very easy - I have often done it myself - to get so caught up into advocating one's position that one fails to see the incoherencies in ones own case.  An old saying is apposite:  There are none so blind as those who will not see.  

When you are making a case to a broad audience as well as to a correspondent -- as is typical in a forum post -- your case is not well served if you refuse to see what all the other readers can easily see.  Denial is not an effective strategy, either logically or rhetorically.