In Ubuntu (GNOME), there is an easy graphical way to disable tapping on the touchpad. However, KDE lacks such a thing. But lacking a graphical configuration tool doesn’t mean this should be difficult. All you need is the gsynaptics package. The package provides a small utility called synclient. Now you can disable tapping by doing
synclient TapButton1=0
To disable tapping permanently, you should use the following to run the command at the start of every KDE session.
echo "synclient TapButton1=0" > ~/.kde/env/disable-tapping.sh