That the errant thief did not go to Purgatory is not a contradiction of the doctrine. Just because the errant thief went straight to Heaven, not all people do. There are many people who may not go straight to Heaven and yet do not go to Hell. God in his mercy provides a place of final purification. The perceived contradictions you claim, if anything like the example of the errant thief, are only perceived as contradictions when the viewed in light of other erroneous doctrines.
There are many scriptural bases for the doctrine of Purgatory. If you wish, I can continue this later and cite those scriptural bases. Right now I have to catch a train!
Very well, Mark, we will search the scriptures together.
The real meat of the objection is the idea that any "purification" remains to be performed. Numerous texts would indicate the opposite, including the one I just quoted: ALL of our sin is cleansed (1John 1:7) by one act of Christ (Rom 5:18). We have nothing to add to that, not even by our torture.
The Purgatory doctrine insults the complete and perfect work of Jesus: it would have us believe that our forgiveness was not complete and Christ's sacrifice was too weak. I will be happy to prove that out a dozen times over.