thats looks dodgey, is there not a safer way?
Unfortunately, the Genieo adware (which powers InstallMac) buries some files deep in the system that, if removed improperly, will cause problems. If you follow the instructions there carefully, it will work. Just don't do what I've seen many people do - ie, don't skim it, assuming you know what it says and acting on what you think rather than on what the article tells you to do.
You definitely should not rely on the uninstaller, which not only won't remove everything, but will also install components if they're not present! See:
InstallMac uninstaller antics
If you make a mistake, there are some recovery instructions at the end of the removal instructions.