Just take a drug legalization. Many Republicans have been vehemently opposed to it. Take a look at the Supreme Court decision Gonzalez v. Raich, where Steve Scalia no less, wrote that the feds could interfere with your growing some plants inside your own home for your own personal use.
Remember that the "states rights" movement started as a response to federal action to end segregation. In my personal opinion, Republicans are just for whatever will push their agenda forward, without regard to the moral or ethical depravity involved in doing so.
Democrats, in contrast, are a bit more principled (in my opinion), especially when it comes to protecting the human rights, civil rights, voting rights, and other rights of the non-dominant groups in this country.