i do understand your feelings at losing the 100% feedback, i myself have it and would like to keep it if possible.
unfortunately as a large volume seller it was bound to happen at some point. but as dave says, negative feedback is often a bigger comment on the person leaving the comment than it is on the person recieving the -ve feedback. annoying though it is.
when i find something on evilbay i want i do check out the seller, it's common sense in this day and age. i actively look for the odd -ve feedback in the hundreds but i'm not looking at the -ve comment, i'm looking at the response to it. your comment back explains that you didn't get a chance to help sort the situation so i would still buy from you and not be concerned, i think most good buyers do this. so i don't hink it will put anyone off, 1 neutral in 945 +ve comments you have no worries.
bearing in mind the prices you sell at is it not worth sending him another set for free on deletion of his comments, not ideal for you and i admit it would be annoying to you but i suppose it depends how upset by the comments you are. although, judging by your post i assume you are upset.
when i need some pace/syncros etc stickers i'll buy from you, knowing that you are poster here is enough for me not to even consider that there would be a problem anyway.
You have enemies? Good. That means you've stood up for something in your life.