Well, their response is something starts out along the lines of “over billions and billions and billions of years . . .”
Ask them what is the growth of the human population ever 40 years or so. I would say it is around 25% (probably a bit higher). Then ask them to divide 3600 years by 40. There you get 90 generations since when many think the flood happened. Take 6 people (3 couples that were still having children). Get an excel spreadsheet in row 1 put the number 6. in cell A:2, write =A1*1.25. in A3 write =A2. Go down to row 90 (generations) repeating this. You get the number of about several billion (people).
What I am essentially doing is simulating the population growth over the centuries.
Now go back to the evolutionist who explain everything slowly changed over millions and billions of years.
Now think about this. If we were around for perhaps 50,000 years and we follow the same idea of what the recorded generation growth has been for the last couple thousands of years would there only be a few billion people are well beyond trillions and trillions of people. The number is so high, I would wonder if we even have a name for it. I doubt there would be any standing room left on earth. Try following the same population growth model for several billion years.
If nothing else, the current population shows strong evidence that there was at least a massive die off of all life on the planet.
One thing too I usually ask is: if the human population just increased enough to overcome disease and war and accidents say at .5 percent, how many people would be on earth today if modern humanity goes back just a million years.
You just provided far more of an argument for the Flood than the author of the article provided against it, which was basically nothing of substance.