I heard he turned around his opinion on Gay Marriage around the time his daughter came out of the closet in 1999, but it was too little, too late. And yeah, King was always a better advocate then policymaker. And, on that last point, he's probably directly responsible for "damm" being considered a specifically-Black swear word to this day.
The words “too little, too late” were my mother’s as well after he died. She said it was self-serving, although I read that the reason he re-thought his stance was because he mistakenly believed it was a choice. When he understood it wasn’t, he came around, albeit somewhat reluctantly, and it’s pretty divisive to this day in the black community (though the harshest critics are usually criticized themselves - Alan Keyes once famously said, “I do not hate homosexuals. I’m not close to anyone who does. I disapprove of the act and the lifestyle but do not hate those who engage in it. I support the Court’s decision to decriminalize the act but do not support making it mainstream. This is how Governor King wanted it.” MLK’s widow was none too pleased about that.)
I was never clear on why she always said, “they changed their ways,” toward Target and Wendy’s but never toward MLK.