Or they suppose that science speaks with one voice, and the only dissenters must be Luddites such as the notorious Cardinal Bellarmine, who allegedly refused to look through Galileo's telescope, whereas the truth is that many of Galileo's assertions, including those about the pendulum, were contested by careful observers, including Descartes and Mersenne, probably the leading physicists of the time.
I'm glad the 'allegedly' is there, even if its force seems partly impeded by the 'notorious'. I've seen this apocryphal story, about Bellarmine refusing to look through the telescope, in a number of places recently. Apocryphal tales generally divide into those we know to be false and those that, despite being doubtful, can't be ruled out; this is very definitely in the former class. We know it is false because (for instance) a few days after Galileo's demonstration, Bellarmine wrote to the mathematics faculty at the Collegio Romano asking for their opinion of the phenomena; in the letter he says explicitly that he himself has seen very marvellous things concerning the moon and Venus through the telescope. (He wanted to know their opinion on whether these and other features of Galilean astronomy were real or artifacts of the telescope itself, which was a very reasonable question to ask.) This apocryphal story, like many others, appears to be a mutation of a prior story, in which Cremonini is the person refusing to look through the telescope: Cremonini, even though he was one of the major Italian intellectuals of the time, is virtually unknown today, but the association of the name of Bellarmine with that of Galileo is relatively well-known, so it is unsurprising that people start substituting his name. Cremonini was very much an Aristotelian, and he and Galileo clashed on the subject a number of times; there is reason to believe that Cremonini is the model for Galileo's character Simplicio. However, Cremonini also seems to have looked through the telescope; we seem to have a quotation from him by a third party in which he said he didn't see anything and looking through the telescope gave him a headache. So it's an apocryphal story about Cremonini, too; one that probably splices together a number of different events into a fiction that makes the point. I don't know of anyone who has traced the actual history of this particular apocryphal tale (which is very tricky to do).
This has very little to do with most of Blackburn's review, of course; it's a quite good review of Sokal's Beyond the Hoax.