My no means do I want to call into question your intentions, which were noble, but the canard that MLK was a Republican is way, way past it's sell date. And I agree with you, having a day to "honor" that thoroughly evil individual next month is abhorrent. The great Senator Jessie Helms knew all that guy.
While it's true that many Republicans are and have historically been horrible, I must point out that the first NAACP President, Moorfield Storey, was in fact a libertarian Grover Cleveland Democrat who fought jim crow laws with libertarianism rather than with statism.
There are people out there who like to claim that the Republican party was "red from the beginning!" and was made up entirely of proto-Communists and actual Red refugees from Europe. While there were certainly people like this, there were also plenty of moralists and conservatives in the Federalist/Whig tradition as well. The Republican party was founded as a single-issue party, so naturally so long as one opposed the extension of slavery beyond the lines demarcated by the Missouri Compromise one was qualified to be a Republican.
I note with some satisfaction that the Nation, one of the oldest and most radical publications in America, was actually originally founded by Grover Cleveland Democrats and that at least one of the Clevelandites towards the end of his life had become a moral nihilist.