Its called faith, and it has always been a part of Catholic orthodoxy that Jesus was FULLY God and man, that is key he therefore had a totally free choice to escape his eventual end, he could have answered the bad thief by removing himself from the cross but chose not to.
I don't disagree with you at all. I relayed the question as I read it on FR, posted by an Orthodox. The question makes sense and I don't know the complete answer (allend gave an answer to which I have a follow up question, see above). However, the fully divine nature of Christ is not part of the question; His humanity is.