If aliens did visit Earth, they wouldn’t necessarily all have the same agenda for Earth; unless they are an actual hive mind, there would likely be separate groups of aliens of the same species with different ideas for what to do with Earth. Even if it turns out that they all want to colonize, they might have different views toward us, and they might end up competing among themselves, much like when different European powers colonized America, for a historical equivalent.
Side note, if they are friendly, I have a feeling that enough humans would consider them to be sub-human that things would turn sour, or, at the very least, they’d decide that we suck and then they’d tell us that we’re on our own. If humans as a species historically can’t treat each other with respect, how would we bring ourselves to treat an entirely separate species with respect?
Another side note, if they want to learn about us, they wouldn’t need to visit at all, they could just send a probe to hack into our internet so that they can join us in our chat rooms from a location elsewhere in our solar system (or further away if they have the ability to send communications faster than light.) Of course... yeah, it’s the Internet.
