Oh man, you said if I argued, I'd be retarded! INSTA-WIN!
Do you have anything to support your claim? If so, you'd be the first, and given the fact that you sound like a pretty angry little girl, I think you could probably benefit from casual marijuana use.
Marijuana does not make someone more likely to do harder drugs. I don't have to prove the negative, you're the one making the claim. It seems FAR more likely that someone predisposed to doing heroin in the first place would start with weed, rather than starting with weed and sliding down into heroin/cocaine/meth addiction. Hell, most kids drink alcohol before they smoke weed, right? Does that make alcohol a "Gateway drug" to marijuana? By your logic, it must!
Again, no. You are wrong and not a shred of evidence supports your claim. Nature/Nurture, read about it. Some people (This is fact) are born with genes that make them more likely to become drug addicts. Others, for whatever reason, experience things that make them more likely to become drug addicts. Since you don't seem like the reading type though, look around you. How many pot smokers do you know? How many have turned that habit into a harder drug addiction?
In fact, according to the CDC, less than 1.2% of Americans use heroin. The last government estimate of people who regularly smoke pot, is around 10%. There are about 315 million people in this country. Do the math.