I don't get what happened. The airline put up a sign saying don't go past this curtain. You went past the curtain. You were surprised when they told you off?
The people in business class (or whatever it was in front of you) have paid more to be less crowded. Therefore the airline puts up a curtain and asks you not to cross it. That seems super reasonable to me.
You don't like the curtain and sign. A reasonable response might be to fly a different airline or pay to get in that section next time.
Deliberately ignoring the sign, going out of your way to tell them that you're going to do that, and then filming the poor guy when he stops you, that seems pretty far off into psycho land to be honest.
In fact, I'm glad that they went out of their way to protect the people in the seats in front of you from being unnecessarily bothered by people like you hiking past.
http://www.nytimes.com/2013/01/29/business/passenger-vs-airl...
In my case they almost apologized for having had Federal Air Marshals detain me.