Y'all: the D in DARVO stands for denial. Sometimes it's sparkling lies, but often time the clinical level denial is real with these folks.
And the -entire function- of denial is to be impervious to facts around whatever they are in denial about.
Debating someone in denial doesn't work. You will NOT be the one person that gets through to them.
-They- have to crack their own denial, and that will involve bigger losses than looking a fool when they debate.
Disempower them in other ways.