The WT teaches that life comes from life.
It also says that scientists may succeed in creating life at some point in the future.
Their argument is that this would only go to prove that intelligent life is required to make life. Life can't arise spontaneously.
The WT does not teach there is a "theological barrier" to scientists creating life as Cofty claimed. In fact it says the opposite, that scientists may succeed some day.
See pages 6 and 7:
https://download-a.akamaihd.net/files/media_books/d0/lf_E.pdf
If you don't accept a statement in the WT as proof of what they believe, then what sort of evidence would you accept?