@Linkat,
I think the objection is that the surface and core of the moon has yet to be fully explored. If the goal of lunar geologists is to study the moon to get clues as to the formation of the solar system and possibly the earth, introducing terrestrial life forms is
pollution, but not in the sense you and Finn are using. More like this second definition:
"To make less suitable for an activity, especially by the introduction of unwanted factors."
They don't want to study tardigrades, they want to study objects in the solar system before they have been influenced and transformed by earthly life. After the moon has been carefully studied and its lunar geology analyzed, scientists and governments may agree on a plan to mine or possibly 'terraform' the satellite but for one country to do this on its own runs contrary to the protocols of space exploration.