You'll need to do more than that to be effective. Find the nearest manager (he/she is the one in the suit) and give him a polite bollicking, telling him that it is putting you off doing any shopping in the store.
I have to agree though. People need to not buy this nonsense en masse for this to work. Otherwise they'll be selling this stuff during the summer next year.
I don't mind this - it means you can get the school shopping done and enjoy the holidays until it's actually back to school time. If people are away in August then they need to get it done before they go.
I saw a full display of Christmas cards in a Dublin city centre newsagent on August 22nd !! I also notice that Marks & Spencer have Christmas wrapping etc for sale now.