I'd like to request that https://history.stackexchange.com/questions/10001/did-joseph-mccarthy-ever-mention-heinleins-novel-the-puppet-masters be reopened. I do not consider the question off-topic and the given reason of "does not merit historical investigation" is simply opinion and borders on the ridiculous. The fact that they were two prominent members of society who were contemporaries with similar ideologies alone should be sufficient grounds for "serious historical investigation".
The year the Puppet Masters was published, there were thousands (if not tens of thousands) of other books published in English. It wasn't even the only SF book with that same theme published in 1951 (see Day of the Triffids). So if this is a good question, why isn't an identical question about Day of the Triffids also a good question? Why isn't another question about any of the other tens or hundreds of books with similar themes a good question? How about thousands of questions about each contemporary book that I can make a tenuous case for being related?
This is why I'd personally prefer to see questions where you have some tangible reason to believe there might be a relationship (heck, I might even settle for "some schmuck in a bar said...". Give me something!)
Heinlein on Mccarthy:
My task [of defending America to foreigners] was made more difficult by the fact that many Americans with other attributes of a horse than horse sense were asserting loudly that McCarthy had indeed created a 'reign of terror.' Are you terrified? I am not, yet I have in my background much political activity well to the left of Senator McCarthy's position. The worst that Senator McCarthy can do to me is to ask me a lot of questions and demand answers under oath. I may resent some of the questions but I can answer them without taking refuge in the Fifth Amendment; there is no treason in my record. [...] I think that a Senate investigation of communism in the United States would have been fought by propaganda just as angry, just as vicious, had the investigation been chairmanned by Thomas Jefferson with Daniel Webster as his chief counsel.
--Tramp Royale, pp. 62-63.
Quoted from here.