Can it be assumed that pooping in safety is common among higher organisms?
If so, then this theory can be applied to the idea of First Contact with an alien species.
Humanity really has no idea what an alien species might be like, how it might communicate, or even how it might act in a First Contact situation. It is entirely possible that the alien would freak out and resolve to eradicate the human race...
Thus it is essential to ensure that the alien being is calm and feels unthreatened before attempts at communication can be made.
In theory, one way to do this is to present the alien with a comfortable and safe environment...one in which it feels so secure that it would even be willing to excrete waste.
An alien bathroom is needed...