Yes we should. I've always thought that if it was clear even if just my country the USA found itself doomed our govt. should take the rest of the world,every nation,every human down with us by any means required. If aliens set their sites upon our planet all govts. should do their best to deny any benefit from aggression. If we cannot have it then no others can. Humans have always destroyed their own resources.burned their homes and crops etc.. rather than allow an aggressor to seize them. It happened plenty whenever russia has been attacked and invaded. They always deny the enemy resources.