Luffy was NEVER scared of Kizaru, stop this nonsense copium
He was surprised Kizaru was coming for his nakama, like Shanks was surprised for Kid about to damage his nakama
Being scared does not mean being weaker. Happens all the time, but saying this is not being worried:
Is the most nonsense copium, imho. As it is trying to divert to his nakama, since he was there to defend them.
Simply, as Luffy said, Kizaru is a really strong opponent that was coming and so he reacted. Happened before, will happen after.