Simply unpack .deb package with

dpkg -x dexter-icon-theme_4.0.0_all.deb $HOME/Desktop 

and then copy $HOME/Desktop/usr/share/icons/dexter folder to $HOME/.icons directory

cp -r $HOME/Desktop/usr/share/icons/Dexter  $HOME/.icons

you don't need to bother with installing of f*cked up deb package...