If we want to be on good terms with space agencies, we have to exterminate tinfoil hat theories ruthlessly.
Note: had the battery been Pu-239 - and a bunch of RTG batteries used in space missions are made from decommissioned nukes, so a person not informed on details of the mission could reasonably expect that was the case - the theory cited would have been quite viable. That wasn't the case, end of story, case closed, thank you.
My opinion is a short, quick and accurate debunking of such stories is more healthy than trying to sweep them under the rug and only give extra feeder to skeptics.
It can be hard to draw the line. Who determines what is a nutcase theory and what isn't?
If the source is notable enough, perhaps some of those would fit on Skeptics.