I dont think that they were right to do this. In the book Wanda said that they had their own planet with their own hosts, then those "vulture" things came and were cruel to them, but they found out they could take them over as well. Anyways, they had their own planet with their own hosts, content. But they went to other planets to fulfill their desires to live a different life. All in all, they did not NEED to go to other planets and take over those planets intelligent creatures, they could of just left it at the vultures. But wanda also said that it was not the same, taking over creatures, on other planets as it was on earth. So I think that they should just leave earth because of all the emotions and such that humans have, hehe.