A man just negayive me for scam. is this a scam?

I have a thread in trade section http://www.steamgifts.com/trade/jhMiC/h-bundle-games-w-4-5-cards-gems-refs-and-offers
and today this man come to my thread and leave a message:
http://i.imgur.com/sRTKVij.png
As I don't have the game, I answered:
http://i.imgur.com/OOUk6Vg.png
The man reply that he want frozen synapse instead:
http://i.imgur.com/jmQ9B2j.png
I answered:
http://i.imgur.com/y2JVfem.png
And of course, spy chameleon is 4.99 euros and my frozen synapse is 22.99 euros, this "game" means other game of equal price. I mean he can trade my frozen synapse with a certain amount of cards or a key of game, but I never said that's his spy chameleon.
The man then add me on steam, here is our chat:
http://i.imgur.com/f0zBGBM.png
Of course I won't trade frozen synapse with him, it's totally not equal, and he say that I try to scam him, and leave me a negative:
http://i.imgur.com/qTks3gR.png
How I scam? I just tell him that he can trade frozen synapse with cards or game, but the "game" is an equal game, I never said spy chameleon for frozen synapse, I never see any of his code, and I even don't have scamed for anything, and he negative me for scam? I think this is really a stupid thing.
So what should I do? Send a ticket to admin? I think this is very unfair for me, scam? I even don't get anything from him!