I'm inclined to agree to an extent, but on the other hand I know children are humans too, and know how I felt about some people when I was around that age.
To have somebody just walk off and ignore it, leaving me to figure out what just happened on my own, would have left me a little confused and sad.
No matter how young you are, getting your first confession stomped on would affect your self esteem/personality somehow. But as I said before I'm more or less inclined to believe that puppy love isn't such a weighty thing.
Either way if I were in the guy's shoes I would've talked with her about it and tried to make it as positive an experience as I could.