I was able to force LibreOffice Writer into light mode by editing this line to the libreoffice-writer.desktop file found here
/home/USERNAME/.local/share/applications/
You can see your available theme names here
/usr/share/themes/
Orig :
Exec=libreoffice --writer %U
Edit :
Exec=env GTK_THEME=Breeze libreoffice --writer %U
NOTE THIS HAD TO BE CHANGED ON 2 DIFFERENT LINES