Think about the following thought experiment and reply to the questions below.

Beings from another planet arrive on Earth aboard a spaceship about the size of Texas. As it turns out, there are approximately 10 million of our galactic neighbors on the ship. Many of us wonder what they are like, but, surprisingly, the travelers from another planet are not much different from us: they are bipedal (i.e., they walk upright on two legs), they have identical physical features as their human counterparts, and appear to have capacities for language and morality (i.e., they speak many of our languages and display empathy toward each other). However, there are some shocking differences: the space travelers are much more advanced in terms of rationality, conscious awareness, and intelligence. It is also clear from the technology they possess that they can do many more things than we humans conceive of as possible (e.g., tele-transportation, mind reading, medical devices that quickly repair injuries to their bodies, medicines that eradicate diseases in seconds, etc). 

The purpose of their trip is to colonize Earth because the planet they left behind is no longer habitable. And because they possess superior mental capacities and technology, they intend to make use of us as their laborers to remake Earth in the image of their former society. They also plan to use us for scientific experiments (given our physical similarities) and as a possible source of nutrition (they really like human flesh!). We may resist, but our efforts would be futile. For the colonizers, the moral arithmetic is clear: harming and killing us humans to continue and advance their own species/society is maximally beneficial.

What do you think about all of this? Would the space travelers be justified doing this? Would it be morally permissible for the beings from another planet to use us as a resource (i.e., a means to an end)? Why or why not?