Gday,
Indeed, I haven't found any evidence that anyone ever doubted Pilate's existence.
What I HAVE seen is many CLAIMS they did before the Pilate stone was found - but no such sceptic is ever quoted or named. The claim is always attached to comments about the Pilate stone.
It seems to just be apologists saying :
"see? Pilate did exist, all you sceptics were wrong about him, you are wrong to be sceptical about other things in the bible too".
I searched through all the old writings and some modern ones, and no-one ever doubted Pilate that I could find :
http://five-essences.blogspot.com.au/2013/09/did-any-sceptics-ever-consider-pilate.html
Meanwhile, I must admit am now starting to be sceptical about the Pilate stone too.
K.
Well there are clearly issues with the Pilate Stone if no independent checks have been made. The only surprise is that anyone would think otherwise.
As far as Pilate himself is concerned - whether or not we can now find any critics who ever expressed doubt over his existence, if prior to 1961 the evidence is supposed to be only those very late copies of writing under such names as Philo, Josephus and Tacitus, then it's obvious that many people might question how reliable that is.
It would hardly be a surprise if people thought the evidence for Pilate was rather scant. And biblical characters supported by scant evidence is not exactly a very convincing state of affairs (imho).