1. Yes, that's essentially what the logical fallacy Cum hoc ergo propter hoc describes.
In other words, if you can't prove causation, your entire argument falls apart, i.e., correlation without causation is coincidental, meaningless and irrelevant, as I have shown in many examples in my previous post.
2. Your argument doesn't even show correlation, because there is nothing in the data set of crime statistics that has a variable that says "marijuana." It's as simple as that. Straight line from point a to point b has no correlation to straight line from point x to point y.
Otherwise, I can make thousands of statements that "correlate" to the crime data which have no relationship to the crime data, except in my imagination - see few examples in my first post.
Really, check the statistics books/blogs on this, because you are confused on what correlation means, let alone why causation is essential for your premise to be even marginally arguable.
And, just for yourself, check again the technology change argument (though I don't claim causation) which has been much more relevant and important in crime statistics than whether the MJ laws have been relaxed (which is destroying the first argument that the "War on Drugs" has failed) or not - they are simply not present in the data (i.e., not a variable in the data, which it can be correlated with).
Maybe this resource on validity and variables can help: Research Methods
I have said multiple times that I'm not arguing causation between loosening pot laws and falling crime, and it is dishonest of you characterize my argument as such.
Once again - is this the 3rd or 4th time? - the point of bringing up the CA stats is to show how questionable is the claim that legalizing pot will cause crime to rise significantly. When you defacto legalize pot in a state, and the violent crime rate goes on to fall by half despite that, it's a strong argument against the claim that legalizing pot will cause crime to rise significantly.
Personally, I would put 1) the internet and 2) the increase in right-to-carry and increase in gun ownership, as major causative factors.
Now please stop mischaracterizing my argument.