First, we will backup our blacklist file:
cp /etc/slackpkg/blacklist /etc/slackpkg/blacklist.old
Mount your slackware install dvd/cd/usb
Navigate to the slackware directory on the install media (you need to be inside the directory that has all the package sets a, ap, d, e, n... etc...)
Then, as root issue this command:
\ls kde | grep '\.t.z$' | rev | cut -d- -f4- | rev >> /etc/slackpkg/blacklist
note the '\' it is *NOT* a type-o! this will add all the packages inside the kde directory to the bottom of your blacklist file.