When talking to non-Catholics who has issue or misunderstanding with what we teach the dogma of Purgatory almost always comes up, if inevitably. It actually very each to get a Protestant who can admit that in their sinful state right now they aren’t able to stand before a Holy God - they will admit that they need to be cleaned up and detached from some of the sins that they are stuck in - they will admit that they need to be purged of some things before they get to Heaven. Most of them agree completely with the process of purgatory, but wouldn’t dare call the process by that name.
Here are some links that use logic to reason through the issue:
davidlgray.info/apurgatoryisreal.html – What is Purgatory, and is it Reasonable to Believe? (mine)
apologeticsfromscratch.blogspot.com/2007/05/purgatory-yes-its-real.html – Purgatory - Yes, It’s Real! (Mark Snapper) - i like it