These beings are professionals, and highly regarded and respected in their own races.
Not just any people of a world travel to other worlds.
Just the representatives and crews do that.
Think about the commitment and dedication it takes to give up your own world and family, to go travel to another world to work there in a crew, to work with many other crews of other worlds.
Think about the process of study and election.
It's a little like saying that in a team of scientists, who join together to go work in a third world country are corrupt.
The alien people are not perfect, but they are openly telepathic, and they do not suffer the stress that leads our own kind to crime.
The alien individuals fly here in their crafts with their respective working crews.
They use large crafts for long distance traveling, and park them outside our atmosphere to live in, and use smaller shuttle crafts to approach the surface of our planet from the larger crafts.
The largest craft is a community craft that belongs to the organization of visiting races.
It has quarters for each of the visiting races... each representative and their crews.