I tend to agree with Sandy. If this was such an important thing for him then he would have been more involved with Nathan's religious upbringing. Not having attended church with them in months doesn't seem to me to project any type of real interest in the religous influence in their lives.
I think what he is doing is trying to shift the attention away from his failings as a husband due to his infidelities and on to you with any kind of mistake he thinks you may have made.
