No I haven't seen the DVD, but I've seen the argument and several variations of it.

1. "How do we know the decay rates have remained constant?" is pretty much the crux of the argument. Ok...it's good to question. So let's look at it.

If the decay rates have changed in the past, what could we look at now to tell that it had happened?

Well, radioactive decay gives off energy in the form of motion of atom and molecule sized particles. That usually means it heats things up.
Radioactive decay now doesn't heat things up much because it happens rather slowly...but what if it didn't? Let's say all that radioactive decay that scientist conclude occurred over 4 billion years, occurred in only 10000 years. That means the heat was released at over four hundred thousand times the rate that it is being released today. I think that would leave a mark. However that mark is not found.

If these folks that know so much more about the problems with radioactive decay dating methods than physicists could show indications that radioactive decay was much higher in the past, then they would have something to criticize those dating methods with. The closest they come to evidence is saying that the decay must have been higher otherwise the Earth would be much older than the Bible seems to say.

Just saying that we don't know what it was like in the past because we weren't there is like saying that we can't know anything about what happened last week or in the next room. Forensic science would not be useful if we couldn't say that the laws of physics were the same in the past. Show that they were not, and then you will win accolades as a scientist.

You can't just say something might have been different, leave it at that and then call that having an open mind.