Why do people say marijuana is good and harmless?

Most people say that because they don't really understand the consequences of using drugs. Though, marijuana is not the most dangerous drug, it still is smoke you are breathing in and there can be traces of different drugs in the marijuana, so buy wisely. Also, only about 10% - 20% of the THC is given off while smoking out of a joint or blunt, so the THC is not the most dangerous part, the smoke is. If you use a vaporizer, there is no smoke but you do get like 90% THC which can be bad. So they are both equally as unhealthy.