Would be handy to have a button on the gang member list page that added all members of that gang to your enemy list
sounds like he makes a few enemies...
What come on, you never had war?
If your at war, you can just click on your gang and it has a link "your gang is currently in XX wars. That would give you the gangs.
But I agree, if there was a section in Friends and Enemies lists for gang, that way you can put in which gangs are your allies and which gangs are your enemies for future wars and to keep "tabs" on them.