If you think about bad possibilities, you can feel intimidated. Clearly fearing aliens, if you assume they exists and could come to the earth, is just fear of unknown. It is actually only possible if you feel comfortable and secure. I heard about thousands of people getting massaccared in Sudan recently. If you were to live somewhere like Sudan or Afghanistan would you fear aliens? Obviously not. But even if you live in a prosporuos country and you are secure in every manner. Still fear of aliens is crazy ridiculous. You will suffer and die anyway. Aliens uncomparably less likely to cause any suffering than aleviating possible suffering in world.
Without much of a thought clearly a world controlled by aliens would be statistically incomparably better than a world controlled by humans. Extreme possibities that can come with aliens are not any worse than possibilities associated with humanity. A fear or dislike of aliens or rather alien invasion indicates all sort of personality disorders. It is also somewhat like fear of God.
And unfortunately if bad aliens come they are not going to ask for you permission. But good ones comes. They threaten them with firing nuclear weapons to other countries. If they are not technologically advanced enough they may just stay away. Or simply they may not care and go away. Although it is unlilkely but it is more likely for humans to get rid of good aliens which would potentially protect against bad aliens. Obviously if there are aliens and they project a potential danger from earth in future they would take control of earth. The ones relatively referred as “good” or “bad” are not necessarily enemies. Bad ones come and wipe out the earth (not necessarily but they wouldn't show mercy) meanwhile good ones stay away and consider risk of threat is negligible. Maybe good ones have religious reasons to avoid harm meanwhile bad ones won't have any reason.