This is a flawed argument. It is the same as the Catholic who invents hundreds of doctrines about Mary and says that just because the Bible doesn't say them doesn't mean that they aren't true. When the bible puts the rest of the universe at the feet of the earth regarding creation, that is all it needs to say. One must reject the whole 6 day creation and substitute some theistic evolution theory to allow any possiblity of importance to the rest of the universe.
Additionally, the quotation of the bible regarding God sending his only son to earth does not preclude life elsewhere. It only precludes that his son (human male child) has not been there - which would be entirely likely if some non-terran life form was not human, would it not? Even the verse from Genesis regarding man being created in the image of God doesn't mean life is terran only.
All I can think to say is that this is like saying, "So other than that, Mrs Lincoln, how was the show?". It is surreal.
Also, please understand I am not debating the validity of your beliefs, or the bible. I am debating your interpretations of inferences.
You are probably quite uncomfortable with the 6 day creation interpretation. Atleast, I assume this. There are certainly a lot of church goers who no longer believe this.
The argument I presented is not flawed. If you want to compare it to someone claiming large amounts of doctrines concerning Mary can be true because the bible does not refute it, so be it. Let's discuss that. Why would that person not be correct in their beliefs?
You also stated I am probably not comfortable with a 6-day creation theory. This is incorrect - God could create anything at any time. How the Earth was created could well be one of many things, including Big-Bang type development, all of which, IMO, do not refute Genesis. I happen to believe that the first four days of Genesis could have spanned a long, long time (no sun, moon, no standard days - I am sure you have heard this argument before).