Scientific illiteracy on full display here. It's obvious you don't understand the scientific method and how it works. If you did, you would understand that it isn't arrogance, It's PROBABILITY. No one is saying that it's beyond impossible for life to have formed somewhere else, what scientists and other professionals are saying is BASED ON THE EVIDENCE WE HAVE ON HAND AND FROM WHAT IS KNOWN, it is extremely likely that our species first appeared in what is modern day Africa. A lot of science is based on probability, because it is rare, and I mean rare for any scientific concept to move beyond a theory, even though evidence points to it being the most logical conclusion. A classic example of this is the Germ Theory of disease. Is it possible that there's another reason to explain disease? Yes, but tens of thousands of studies have indicated that microorganisms exist, their replication in hosts are usually the primary cause of disease and by addressing those organisms, you stand the best chance of curing, or mitigating said diseases. So, when you say a scientific theory is just a theory, you are dismissing the amount of research, the amount of data points needed to get to that level.
Then again, we live in a society where nuance and logic are frowned upon, so there's that.