Well, at least when it comes to some things, he is either abysmally ignorant, or deliberately untruthful, and for the sake of giving him the benefit of the doubt, I will say he is ignorant. He seems an honest enough guy. But about what things in particular is he abysmally ignorant, you ask? Well, things like Intelligent Design. He has been very outspoken on the subject, and I can tell you he doesn't seem to have the faintest clue about what Intelligent Design really is.
There is a YouTube video here, among other places, where he gives a talk about Intelligent Design, essentially telling people that Intelligent Design is a 'god of the gaps' argument, as it is commonly and erroneously described (especially at Wikipedia, but no surprise there). The argument goes like this: “we don't know how something works or has come about, therefore God must have done it.” He gives examples where some very prominent and well known scientists have apparently reasoned that way, with Issac Newton being his prime example. He states that when these brilliant men understood the law-like nature of the world around them, they could describe it without referring to God or gods. But when they reached the limits of their knowledge, they invoke a god or gods to explain what they could not with a naturalistic explanation. And I can see how that can be a big problem, and that it very well could in fact cause people to prematurely give up searching for an explanation for some phenomenon that is under investigation.
But I also see another big problem: Intelligent Design is nothing of the sort. Intelligent Design, as a scientific theory, does not in any way resemble the 'god of the gaps' argument. There are many places to go that will give you a solid definition for Intelligent Design, and the 'god of the gaps' description is nowhere to be found within these other sources (New World Encyclopedia is one of them). And yet over and over and over, Mr. Tyson, in his presentation linked above, gives examples of the 'god of the gaps' argument, then says “this is intelligent design!” It could be that Mr. Tyson has been enlightened since his talk at the Beyond Belief '06 shin-dig, but if he has, I am not aware of it, nor have I heard him retract his former statements.
But if it's not a god of the gaps argument, then what is Intelligent Design? I will quote form the New World Encyclopedia:
Intelligent design (ID) is the view that it is possible to infer from empirical evidence that "certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection" Intelligent design cannot be inferred from complexity alone, since complex patterns often happen by chance. ID focuses on just those sorts of complex patterns that in human experience are produced by a mind that conceives and executes a plan. According to adherents, intelligent design can be detected in the natural laws and structure of the cosmos; it also can be detected in at least some features of living things.
Why this is controversial is astounding to me, because people make design inferences all day long without even thinking about it. Every time you see something like this:
you automatically 'know' that an intelligence was behind it. You didn't see anyone do it, and you don't have a clue why they did it, but you automatically know that someone did it. These things are obviously best explained by an intelligent cause, even though we know nothing at all about the nature or intent of the creators of these artifacts when we first see them (i.e. who did it and why), and in many cases, we don't know how they did it. But that doesn't matter, because as soon as we see these things, we immediately abandon any notion that they were produced naturally by some weird, freakish natural phenomenon that has so far eluded the scientific community. In fact, to suggest that these artifacts were the result of wind or erosion or some such thing would be quite a stretch at best (but most would consider such a notion absurd).
But if this is the case, that there are things in this world that are best explained by an acting intelligence, and we actually conclude that every day, then it seems to me that there should be a rigorous way to describe why we reach that conclusion. This is essentially the effort behind the Intelligent Design movement - to be able to explain why we know that the three examples above were made by someone. Hence, ID is a rigorous philosophical and mathematical method by which we can conclude that certain phenomena in our world are best explained by an acting intelligence. It is the answer as to the 'why' we believe that the three things above were made. Or in other words, if we tacitly reach these sorts of conclusions every day without thinking about it, then we should be able to explicitly reach these sorts of conclusions by thinking about it, and we should then be able to apply that reasoning to everything around us, including living things and the universe as a whole (e.g. Dembski's 'explanatory filter'). That is at the root of intelligent design, in a nutshell. Pretty simple, huh?
But Mr. Tyson is a really smart and well read guy. Surely he is privy to such a simple concept? Alas, I guess not. It is another sad example of an ID antagonist either not doing their homework (which is shameful for someone of his learning), or he is an outright propagandist and distorter of the truth. It's one or the other, to be sure.
To wrap it up, in an effort to address Mr. Tyson's assertion that ID is a 'discovery stopper', I would only ask this question: if it can be shown with rigorous deduction or powerful inference that biological life or the universe as a whole has been designed (which is what ID claims to be able to do), then what is the point in continuing to look for a naturalistic explanation, other than to try to maintain the hope that God does not exist?