Conservatives can easily get into the mold of telling everyone else what to do just as the left does.
The drug lobby wants to keep pot illegal so they can continue foist deadly, addictive meds on the populous for the reason that only they can produce, sell and profit from highly controlled substances. (Legal sales of pot are only the beginning to growing your own.) Pot would wipe out the antidepressant business as well as much of the pain killers.
If that's different in other States, well, States Rights right back at ya'. If some State wants to stand anyone caught with pot up against a wall and shoot them, that's also a State's Rights instance. Works both ways.
Some sane policy with regards to the line between someone with a stash for their own use and someone dealing with a misdemeanor for the former and felony for the latter consistent across the country is better than a patchwork quilt in this case. That's Federal decriminalization of use, not an infringement of State's Rights since a State could bring State charges rather than Federal Charges. So, yeah, if you let the knife cut both ways, it's a State's Rights issue. If you dictate decriminalization, you're no different than the people on the other side of the fence.
While I don't care about either casual or total drooling idiot pot smokers, I do care about what the proponents of total legalization will claim legalization of pot "proves" about any and all addictive drugs now in existence or dreamed up in a lab in the future.
I also get a kick out of the "free society" argument that always revolves around dope, prostitution, and all sorts of perverse sex or porno.
And don't bother with the "slippery slope" being all BS, either. If you can look at the little court cases chipping away at our rights over the past sixty years and not see how that gradient is created you're blind.