That is just so typical of you Trump supporters - you resort to mockery when you can't respond on the merits.
I'll explain this in simple terms:
If you take someone else's property (regardless of value) without the person's permission, that is larceny.
If you do so through the use of physical force, that is strong-arm robbery (though different jurisdictions use different terms--off the top of my head, I don't know what NY calls it, or if it's just a different degree of larceny).
If someone commits (or attempts to commit) larceny, the victim has the right to use physical force to prevent or stop the larceny.
Here, the security guard stole the protester's property (the sign). That's larceny. He did it through physical force (ripping it out of the protester's hand). That's strong-arm robbery. The protester tried to stop the security guard by grabbing him and trying to take back the sign. That's justifiable use of (minimal) physical force.
That's not ridiculous. That's the law, in New York and pretty much everywhere else.
Actually, I'm enjoying watching you write fantasy mini-novels regarding "larceny" and "strong arm robbery ... off the top of your head."
Please continue... then call the NYPD.