Trust me, I'm well aware of the definitions of conservatism. Republican has become synonymous with neocon these days. Hence Mccain, who has adopted the neocon platform since he decided to run for president, and even moreso when he emerged as the frontrunner.
Decriminalization is not a conservative cause, its a libertarian cause. But since conservatives are in favor of decreased government control over our lives in many cases, it also is a cause for some conservatives. there are plenty of conservatives who don't agree with decriminalization. It can also be a liberal cause, because it is a progressive step that would result in a lot less people being locked up in our incredibly shitty prison system. And also, plenty of liberals don't believe in it. This is all just labeling anyways.
I pity anyone who is 100 percent democrat, republican, conservative, libertarian or whatever. Our politicians represent us to some extent, but will always be influenced by special interests.