As far as I can tell, these tribes aren't indiscriminately aggressive: they do take your fame into account. However, they are quicker to attack than normally.
All the tribes I have positive fame with did not attack me; the Water Breakers (+30), Frahar Hunters (+30), Barkers (+35) and Dune Riders (+4) all left me alone. But all the tribes I have negative fame with did attack me, including the Renegades (-25), Watchers (-25), Lawless (-50.00) and Scorchers (-50.00)
I would recommend everyone stay away from these tribe expeditions if they have negative fame with the tribe.
All the tribes I have positive fame with did not attack me; the Water Breakers (+30), Frahar Hunters (+30), Barkers (+35) and Dune Riders (+4) all left me alone. But all the tribes I have negative fame with did attack me, including the Renegades (-25), Watchers (-25), Lawless (-50.00) and Scorchers (-50.00)
I would recommend everyone stay away from these tribe expeditions if they have negative fame with the tribe.