Ramming or trying to Escape

Why is the assumption being made that the Promo is intentionally ramming the SJ ship? And not the SJ ship it trying to stop (get in the way of) the Promo? The Promo wants to “Get us out of here” could be out of a cave or off the planet. Not 100% clear. “There is not going to be an Earth to return to” doesn’t necessarily mean the SJ are about to Fly to earth to do something destructive. Maybe something else. “They are leaving” (The SJ’s) may be because they know something uncontrollable/dangerous has been unleashed.