Why is it that many conservatives are against marijuana but also against gun control and the libs vice-versa?

Is it not pretty much the same principle? Marijuana, not everyone feels that it is safe, the same can be said for guns. If guns were illegal, it wouldn't stop criminals from getting them and criminal gun rings would flourish, giving gangs more money to do whatever they see fit. Isn't that what the Mexican gangs are doing with marijuana? I just don't see how you can really be for one and not the other when we still are unable to control things like gangs.