Maybe he means that desires to do wrong things are possible in the current fallen natural state of mankind. This is not anything that is theologically disputable anywhere in serious Christendom.
Apply a selective mask to that, and you can make the observation look like doing wrong things is natural without any of the other context.
Nobody asked whether the natural is what we ought to be focusing on, and quite frankly that does seem to be the bent of some Christian followings. Natural law! Well the problem is, we can’t take that, whatever it does mean, as meaning the natural is our law.
Neither is normal our goal. Normal is too little. If achieved it would only glorify our fallenness. We are desired by God to be on a journey to heaven, and any lesser view is bound to disappoint.
Longer response: the scientific, descriptive idea of “natural” is by no means identical with the Realistic idea. In the Realist view, one could say that every crime is a crime against nature.
So, I want the caffeine buzz and restful sleep, the chocolate pleasure, but not the waistline, the fondling and the embraces and orgasms, but not the relationship and puppies. I neither KNOW nor DESIRE wholeness; or rather I want it while I also want to dis-integrate things.
Who will save me from this body (and psyche) of death? Thanks be to God through Jesus Christ our Lord!