Dear Cinnamon,
For heaven's sake (literally) they didn't CONVERT. Wasn't that rather obvious, even before their rescue? Are you kidding? They said what they had to in order to survive. And, were you privvy to their potential inner communications with God before or during their parroted words? I thought not. But even so, you feel they are not "good" Christians? Well guess what, most Christians are NOT, certainly not all the time -- most definitely including me -- and it doesn't take a gun to my head to bring out disappointing actions in me, sadly.
Perhaps your sins are truly far less in number and in human perception of "badness" than mine and theirs are. But as I recall, most of those "wonderful examples" you refer to that are in the Bible, also out and out screwed up royally in addition to their best moments. Did they disappoint you too? Don't you see that we are all disappointments in that way, Cinnamon? I do not at all mean to be rude to you -- I just find it so hurtful that you would take this unbelievable moment of their lives to say judgmental things about these men, that I am defending them.
If they are indeed Christians to begin with (personally, I am factually unaware of that, either way, but IF they are -- ) we are all going to the same place anyway, and thankfully, our God won't be comparing our past sins on earth to one in other the way "we" sometimes do -- especially not judging the worst moments of one's life as necessarily conclusive and definitive.
I know we are all so relieved and thankful they have been released -- AMEN!
It specifically states in the bible, if you deny before men, I will deny you before my father who is in heaven. Orally converting to Islam is an indirect denial of Jesus Christ as their Lord and Savior. But, we have a forgiving God and I believe he will forgive him. But, there may come a day when we have to choose as stated in Revelations, and during that time, names will be blotted from the book of life. So, this decision appears to be a very serious one before God. May we pray for grace and a strong commitment with Him.