Does the other person have an official diagnosis? "Agree to disagree" may be helpful in that case, although it doesn't seem like it from the response you received.
My xwBPD does not have an official diagnosis and any of my attempts to say we have different views of the same event, etc. have only served to enrage her further. I've found the only thing that works to de-escalate is to go no contact with her. Which doesn't really work if it's someone you in a relationship with or have to maintain contact at some level.
Personally, I would be very concerned by someone stating "the actual truth really makes no difference" as that indicates they are only going to follow their emotions/perceptions on a given subject, which may very well not be grounded in any sort of reality. This could quickly get into real danger territory.
If you have any concerns, it may be time to keep a journal and even video/audio recordings.