Other easy way is instead of argueing with him, give him a option to cancel the order while opening a dispute. If he accepts the feedback will become void.
Leave a followup up reply for his feedback (the message should be positive for other customers who reads your feedbacks, if you use negative words again it is not good for your reputation).
For your feedback followup sample --
"Kindly cancel the order no problems"
"Dont worry we can cancel the order"
"Kindly pay for next purcase"
Use kind words like Please, I request, Thanks, while writing email to him, he will agree.
What to do eBay is really strange business. We have to manage solve the problems like this. If you have a shop in the street, you have to face more problem than eBay business.
My personal opinion is your feedback rating is good, in 1 week it will go to next page.
I can say 99.99 customers are really very good in eBay, 80% of the experienced ebayers dont even ask a question, they just buy, pay and leave feedback after receiving item, they are Gems of eBay and they dont waste our time.
You can also block "Jay" bidders like, those with out phone registration and 2 unpaid cases in previous month can help get rid of people wasting your time and money.
Goodluck.
Thanks and regards,
CoolBrasCo.