Because today, a number of conservatives will try to pull a misdirection by claiming that Martin Luther King was a Republican. Look at the issues Martin Luther King advocated for in addition to civil rights, and then try to tell me which Republicans today are advocates for the same issues. It's a curious historical revisionism that is being played out today by some in the right, with the goal to convince blacks that "the real racists" are those of the Democratic Party. To believe this, you have to ignore all history from 1950 to today where the racist Democrats of the South who voted against civil rights legislation eventually switched parties to become racist Republicans, some by way of the Dixiecrat Party. You have to forget the fight in the 1980s by many of those Republicans to stop the creation of a holiday in his honor . It would be funny if it wasn't so brazenly shameless and sad.