Do you really believe that it is yours to do as you want with it?
Do you really believe that we cannot claim it?
Because you are already here?
Does not your own history show otherwise?
I would ask you what would you call colonialism?
Is it not a foreign government or people seeking to extend or retain its authority over other people or territories?
Have not your colonizers imposed their religion, economics, and medicinal practices on the indigenous people?
Have they not done so in most cases for their own selfish interest?
Have you not expanded into areas where different animal species have thrived for years and hunted them into extinction in some cases for no other reason than sport?
Do you not feel you are justified in doing so because you have determined that you possess the superior intellect?
I would argue that when compared to your own history it is easy to appreciate that the takeover of your world by the Association of Developed Planets is in your best interest.
You have chosen to ignore the warnings from your own planet that you are doing irreversible damage to it with little or no regard.
You have chosen to overhunt what you deem lesser species instead of looking of looking to create equilibrium with them. As result you have destroyed ecosystems with little or no regard.
Our takeover will bring a halt to these and many of the other destructive practices that you humans practice. In essence we are saving you. We do this because despite your flaws because why you are not currently worthy there are those among us who believe that you are an intriguing species who given the proper guidance can mature into one of us.