I think the real issue regarding Pilate is the paucity of evidence for his existence. Until the discovery of the inscription, there was nothing available about Pilate other than a few written records.
This relates to the argument from silence often used against the historicity of Jesus: even a ruling official such as Pilate left little evidence of his existence; expecting such evidence to exist for an historical Jesus is, therefore, rather unreasonable.
In fact, the argument can be turned around and framed in a different way. As you said, no one ever seriously doubted the existence of Pontius Pilate; yet before the discovery of the stone bearing his name, there was about as much evidence for Pilate's existence as there is for Jesus' existence,
especially when we adjust for their relative political and social stations.
The ahistoricists set their criteria of evidence in the case of Jesus unreasonably high. Many are otherwise reasonable people, so one can only wonder that they do this in order that they can intentionally prevent their criteria every being fulfilled and remain convinced of their ahistorical position.
Jon
Love your enemies!
™ Version 4.2