You're correct about the rule, however we can't say that a verb is always stative, because it depends on the exact meaning. In your example, the speaker wants to emphasize that he is *actively* hoping, almost like praying, or that his hope is influencing his actions. Another verb used this way is "to like." If we say "I'm liking this," it means that I'm actively enjoying this. And then, there's the Scorpions' hit single "Still Loving You" -- but that's perhaps more an example of poetic license.

It's not only in films that we use this. It's the present continuous or what we in America also call the present participle. All of these are 'state' verbs or 'state of being' verbs: I am thinking... I am hoping... I am longing... I am eating... etc. And past continuous: I was hoping... I was eating... etc State of being verbs are extremely common in English. It's not slang. It's just a standard part of English.