Nonetheless, it is settled law. I do believe that it happens to be good law.
The Bill of Rights has to extend to the states, otherwise it is meaningless. Prohibiting the Federal Government from banning handguns is meaningless if the states are allowed to ban handguns. Prohibiting the Federal Government from shutting down oppostition newspapers is meaningless if the states can shut down opposition newspapers.
Either these are rights retained by the people, or they are not. If they are retained by the people, the state can no more infringe upon them than the feds.
The 10th amendment address powers "retained by the states respectively, or the people." An example of a power retained by the people would be to enact a ban through referendum or state constitutional amendment (or through lobbying their state legislature) on homosexual marriage. However, the homo activists are attempting to get the courts to dictate that some heretofore undiscovered right exists within the constitution that would prohibit this power of the people via the 14th amendment. (Apparently your fondness of Marbury would support such a judicial dictate.)