Marijuana has been proven to be a gateway to using other drugs.
No, that has not been proven. Perhaps, there's a statistical correlation but correlation does not equal causation. No study has come close to showing that marijuana use causes hard drug use.
And as for gay marriage, I support equal rights for homosexual couples, but don't redefine marraige to do that. Call it a "civil union" and give them the rights, but don't be changing a religious definition.
How does changing the law change the religious definition? We have a separation of church and state and ultimately, nobody can force you to support gay marriage. And really, if it's the same in everything but name, doesn't that imply gay people's relationships are lesser compared to "real" marriages.