"But the fact is that this material fell down on Earth, and similar if not identical material has been falling onto the Earth for its entire history."
"Understanding the origins of that matter is inherently tied in with understanding the origins of life."
non sequitur
No, not non sequitur, but the inference of pan-spermia is only one of a number of possible causalities for the origin of life.
It is a presumptious set of statements, that I'll grant you.