That was just a simple explanation but should be enough to tell that Hackers are healthy, Crackers unhealthy.
that's only partially true, well, depending from which point of view

crackers as opposed to hackers, yes, the are evil, mostly use tools they dont understand to gain access to a system (script kiddies). but there are also a different kind of crackers which im very fan of: copy-protection crackers, i love them. the silliest copy-protections are inventend by even sillier companies which they sell for the most silly prices to software manufacturers, just to see it cracked even before the software hits the stores
why i hate copy-protection? not because i do not want to buy the game (i buy most of them), but because im sick of paying 40$ for a game and then not be able to install it because of the CP - most prominent for such "behaviour" is surely starforce. nevertheless, companies are still trying to "protect" their goods with that bull, and cracker will hopefully always try to crack that.
[ Edited for language. --Karyuu ]