What is a REASONABLE punishment for this or is it even punishable?

[An Unknown Kevin]

I posted a thing on Facebook about a weapon in a video game called Battlefield 4 and said it was useful in the game, and I made a joke out of it because my friends hate the weapon in the game. I said: "This is your worst enemy but I find it useful." And then I tagged my friends. Now here is where it gets bad: My uncle saw it and contacted my dad saying I was threatening people with it. (No threat was made and my friends understood the joke and one even commented about it.) And then my uncle called the police. The police called and I told them about the post and that it was a video game and I meant no harm by it. They then saw no harm and said that no further action was going to be taken. My dad said I was grounded for a year. (no Xbox, phone, or social activities with friends) I think a week or two would be reasonable, but a year??? I have all A's and I try to be a good kid and yet my dad always points out my flaws. Is this reasonable or what should the punishment be? Honest opinions please

Link to the picture I posted: http://bf3blog.com/wp-content/uploads/20...nger-1.jpg