I would certainly object to Dr. King's infidelity being used to conclude that he was not great or his messages were not profound.

As you say, heroes can be both great and flawed. Almost everyone is.

It doesn't, however, follow that we need to emphasize the flaws. Accept they're there, of course; talk about them when relevant, absolutely.

But I don't think it's beneficial or virtuous or even particularly honest to pump up the flaws beyond what is necessary. There were millions upon millions of people with comparable flaws, yet we don't talk about them to set a baseline for comparison. There were not millions upon millions of people who gave us clear and compelling ideals and motivation to seek them.

It's not advisable to put even our heroes on too high a pedestal, but neither should we dig a hole for them.

"Mr. Luther King Jr., adulterer and civil rights leader" is a perfectly awful description. I do, indeed, object to that.