Can Church A Badmouth Church B?

There are four possible scenarios: 
Church A - The church
badmouthing Church B
  Church B - The church suffering
the verbal attack

Scenario One:  
Church A and Church B are both
true churches of God
Both churches are owned by God and peopled by individuals God called there.

     

Scenario Two:  
Church A is a true church of God
and Church B is not
The true church has no biblical mandate to attack a false church.  Anyone can attack a false doctrine regardless of who teaches it, but they cannot attack the congregation or leaders.
 
     
Scenario Three:  
Church A is not a true church of God and Church B is
This type of attack is prophesied.  The true church will experience hate, condemnation, slander, bitterness and even murder as we enter into the end times.  I would personally hold as suspect any church bringing slander and condemnation against another church.
 
     

Scenario Four:  
Neither Church A nor Church B
are true churches of God
This scenario is rather moot.  Even so, even a false church, with a nominal belief in Christian principles could not find justification for attacking individuals and other churches. 

     
As you can readily see, there is no acceptable scenario for any church A to be attacking another church.