It is best not to compare it to other things and leave it at that. I have actually seen many folks completely screw themselves up with weed. I'm not saying to demonize it or anything, as I enjoy it myself. Only that weed, like anything, can be abused, and have extremely horrible effects on certain individuals. When they say you can smoke yourself retarded, they aren't lying.
Everyone is different, and it is just annoying when some people act like it is some cure-all for your problems, when in reality, it has the potential to ruin some.