because its human nature to feel a sense of unease or discomfort at being forcibly place in an unexpected situation like that. While I think "fear" is too strong a word to use in this particular example, its still something that a lot of people don't have a lot of experience with
Like anything else, you can't expect someone to behave any certain way in that situation cause everyone is different, especially if its the 1st time its happened to them.
If anything, I'd say for the most part his reaction was quite average for the average guy. Some particularly unbalanced individuals may have reacted negatively and aggressively towards the person in question