Well, if it is the case that he at first refused to intervene, and the dispute was over 1 year old, then he later intervened with a negative directly after you refused to trade with him, that seems like poor judgment.
This has nothing to do with the personal dispute which happened some time ago. This person (currently ignored) is acting like a special snowflake. I've left several ratings recently as I've caught up on that (still a long list to go). The reasoning: "We had a dispute X time ago, and you aren't allowed to leave a negative rating ever" is bullshit. Don't get me started on unjustified retaliatory feedback, which should make one less trustworthy by default.
Seriously, you're 1 year behind on providing feedback? And you're feedback for defcon is negative, but your feedback for QS is neutral? I appreciate your contributions to the forum, but I find the feedback you're leaving questionable and therefore worthless to me.