It would have been better to create a holiday called "Civil Rights Day," to honor King's accomplishments, and the accomplishments of many others. Perhaps that change can still be made.
The holiday for MLK came with bipartisan support in the early 1980’s including Ronald Reagan.
The lone voice against it came from Senator Jesse Helms of North Carolina. Another reason liberals hated his guts.
I’ve read that conservative Governor Meldrim Thompson of New Hampshire communicated his concerns about naming a national holiday for King.
I assume Thompson’s concerns were over the left-wing connections etc. although the conservative movement of the time was aware of this problem in at least a general way.
Reagan is said to have acknowledged Thompson’s concerns but his action was to join the overhwelming Congressional support for the King holiday.