Can I reply to negative feedback someone gives me on ebay?

[staycoldB]

I sold some shoes on ebay and 3 weeks later this moron is messaging me saying the shoes have pebbles in the soles and the suede is discolored and that I rated them higher than the condition that they're really in and that either I give him a 50% refund or he's leaving negative feedback. The idiot has had the shoes for 3 weeks before trying to extort money back from me. If he leaves negative feedback can I reply to it pleading my side of the story????
Thanks for that link, but I need to know if I'm going to be able to reply to his negative feedback and give my side so future buyers know I'm honest. I have 100% positive feedback and this is BS if this prick can do this.