One of the main recurring arguments against legalizing marijuana is that it is a &quot;gateway drug&quot;: people who try it are more likely to go on to harder drugs like opium or cocaine. This means that some people legitimately believe that legalizing it would get more people into these other drugs and increase the overall number of drug crimes.<p>It doesn&#x27;t really make sense to me, but it seems to be one of the most common rationalizations for being against legalization.