*Deep breath*
A factory takeover is always a peaceful, organized process if the profiteer being deposed has the good sense to gtfo, and doesn't call in the riot cops, instead opting to let the rightful owners, the workers, take over.
All right, we'll start with the easy one.
What makes them the "rightful" owners? There are only two ways to legitimately acquire property:
Original appropriation (homesteading), or voluntary purchase.
Secondary appropriation, or "squatting" is only valid on abandoned property. Certainly you're not claiming that the factory owner (or shareholders) abandoned the factory?
Use determines utility. Who uses the factory? Workers? They own it.