I think the question he raised is quite relevant. It's a given that the government might have to take extraordinary steps. For example, on 9/11 the vice president gave an order to shoot down any commercial planes still in the air. It's a horrifying prospect, but it was absolutely necessary and appropriate given the circumstances. No one is arguing otherwise or asking the current president to rule out an action such as this.
It's a given that if you're posing a clear an immediate threat that you are liable to be killed on the spot- let's say if you're waving a gun in public. The question about drones isn't about these immediate threats- it's about whether or not the executive branch can use drones on US soil against someone suspected of terrorist activity, but not actively engaged. Let's say for argument's sake that there's a tremendous amount of evidence that this suspect really is a terrorist, and either has carried out an attack or is planning to do so. Would it be constitutional for the president to authorize a drone strike on that person while he's sleeping, or spotted at a cafe?
It's a fairly straightforward and relevant question that I really do think deserves a straightforward answer, and so far the president and his CIA nominee have declined to answer. If the answer is no- that person would be apprehended and put on trial- then it seems to me it would be a noncontroversial statement. If the answer is yes, the president can do that if he deems it necessary- then it raises other questions about what, if any, are the limits to the executive branch's power. But at least it would be an answer.
I'll also add that I do not think this is a partisan issue- Democrats, Republicans, conservatives, liberals, and most everyone in between has common ground here. I think the response from many, including on this forum, would have been much different if George W. Bush had dared to assert his power this way.