If we assume an individual, call him T, decides on a course of action and justifies that action by knowingly referring to wrong or misleading information is the action for that reason alone morally unjustifiable?
If having undertaken that action, it is then proved that a case could have been made, but not the one actually made, how does that affect the validity of the action taken?
If in taking that action T knew of the real facts which post hoc can be used to justify it, but chose to rely instead on misleading or inaccurate information what then?