I don't understand how "all drugs are inherently bad". That's like saying money is evil because it causes a lot of problems. Not all drugs are used for recreation, and sometimes one can save a life. Morphine, oxycontin, percocet, aderall, benzedrine, seconal, THC, etc. can alter perception or behavior, but that doesn't make them "bad" by nature. The intent means the difference between proper use and abuse.
Like most psychologically addicting things, weed can become a crutch. Some of my friends who smoke became potheads, and others not. I've also seen friends (who never touched the stuff) drop out of school or lose a job because they spent all their time playing Counterstrike or WoW. To me it seems more of matter of discipline and moderation than the actual pastime in question. Of course, the same can't be said for physically addictive substances (caffeine, heroin, etc).