"Most species have died out due to evolution of superior competition or climate change."
An impactor which is +20 miles in diameter is "superior competition" & and would alter climate. Such large rocks would be rare in our particular slice of time, but during the time frame of the evolution of life they would occur.

"The impacts of climate change on current populations are readily apparent and the fossil record is clear that there have been many large changes in climate. Species go extinct continuously not just during mass extinctions of which some, many, or all may be due to impacts."

Mass extinction is probably what Peiser was referring to when he said "wiped out". I believe Peiser's point was that impactors have played a major role in the evolution of life; this new paradigm will develop over time.
I would say that large impactors have dominated evolution and geology of our planet. Smaller rocks (mile or less in diameter) have also influenced life and human culture.

"There is also evidence that some large impacts did not cause mass extinctions, a lack of craters corresponding to most mass extinctions (may have been obliterated by time), and nonimpact explanations for some mass extinctions so there is by no means any consensus that even large mass extinctions are mostly due to impacts."

I wouldn't be surprised if there was a mass extinction event from a nearby star going supernova. We certainly don't have all the answers, but over time, impactors will probably be a major part of the puzzle pieces.

"Authoritative and incorrect blanket statements such as this from Peiser who has no relevant training or experience in terms of paleontology or biology is is one of several reasons I no longer routinely visit CCNet.

At least he does a good job promoting the serious potential issue of impacts, but his willingness to jump in front of front of those with more expertise (and I'm not talking about me or Grondine for sure!) as a public mouthpiece for the issue also irritates me."

Yes, we all know that the scientific process irritates you.
:)