This is the point, where you normally describe how you solved your problem.
For everyone else, this is how you do it:
You have to edit the 'Behavior - Response' field of a unit. It's normally set to 'aquire', which means it attacks the enemy unit. Without an attack this is not possible anymore, so the option 'flee' is used.
If you want your unit to do nothing, just set the field to 'No Response' and you are done!