With the caution that you want to be vary sure you are in the correct directory (because this could erase your entire system if done incorrectly, so make sure you have a backup!):
(or the directory where you run Fritzing from)
(optional but wise)
(to make sure you are in the Fritzing directory where you think you are)
rm -r *
(this is the dangerous part as it will erase everything below this). That will remove all the Fritzing code and a new tar will do a new install.