So, it’s the day after the nuclear apocalypse. At an android factory, a group of androids are planning to create a new community. This community is integral to the plot of my story. Fresno, were the factory is, is supposed to be a human free zone that only the occasional merchant and trader travel to. In the past, the robots gathered collections of weaponry and chased all the humans out of town. The robots are usually emotionless and stoic, and never use violence unless necessary for self preservation. What might be a plausible reason why the androids chased the humans out of town?
Like you said, self-preservation. Even if humans are weaker or less intelligent than the androids, their emotions make them a threat. Especially true if the humans have much greater numbers. The androids may see it as safer to expel all the humans rather than risk any chance of an anti-android pogrom.
Remember, being stoic and emotionless doesn't necessarily mean noble. Sure, they won't hate humans, but they won't have any compassion for them either. If their cold calculations show humans to be more trouble than they're worth, they won't hesitate to banish or kill them all.