Actually, you did imply that you knew their reasoning, and that their reasoning was to celebrate based on his guilt. Even just now - "They gave a hero's wecome to a mass murderer." implies they believe he is a mass murderer.
Please dont tell me you can't see the difference between "They gave a hero's wecome to a mass murderer" and "They gave a hero's wecome to a mass murderer they believe is innocent."
The first article actually has a few of the victims families saying they think he's innocent, btw.
Either way, if they are celebrating because they believe he did it, they are sick. If they are celebrating because they think he his innocent, their celebrations are in poor taste.
As I said above, it would be in poor taste - but very different from celebrating their return if we thought them guilty.
Face it, you're just trying to say "All of Libya supports terrorism!", when you also admit you "dont know their reasoning".