indefensible

adj

1. Not defensible; not capable of being defended.
2. (figuratively)Not capable of being justified or excused.

   “Mr. Elliot's frank statement that "sloth and untidiness are indefensible" is a sign that the task will be tackled with vigour.”

   “The president evidently intends to follow his own misguided calculus. A decision to withdraw would be indefensible. It is important to understand why and to consider what we need to do next.”

   “Killing civilians is indefensible, whether done by Hamas or Israel [title]”

3. Incapable of being explained.