I'm not gonna condone Maher or anything - it was a needless and insensitive remark - but in a broader, linguistic way, I'm very skeptical of this "that's our word and you can't have it" mentality. Language doesn't willfully align with people's desires. There are very likely words in English that were borrowed from other cultures, words that those people didn't want other people to have, words that had harsh meanings that were eventually altered or neutered as they passed through time and among cultures. Languages evolves and shifts hands, whether we want it to or not.
I mean, no one bats an eye at phrases like "that was a total cakewalk", even though the "cake walk" is steeped in racist history. People divorced the phrase from its origins and converted it into something more broadly usable. Is that right or wrong? It's an interesting question, but it is nonetheless what happened. Pragmatically, that's just how some words survive.
The n-word isn't a special case. It's a word with a lousy history that could be repurposed as people deem fit. Black people claiming it as "our word" is, in itself, a repurposing effort. And there's really nothing wrong with re-appropriating and redefining troubled words. But I feel like maintaining this harsh line in the sand regarding the word only makes the conflict in the word more salient.
And in another way, this isn't really about the n-word, as much as it is the fact that American society hasn't sufficiently divorced itself from the pain captured by the word. I feel like that's the part white people often don't understand - for them, it's just "why do Black people want to feel included in society, and then exclude us from their language? That's not fair". But the ongoing prevalence of racism means that Black people can't get away from the negative connotations of the n-word. It hasn't become like words like cakewalk or loophole - sanitized of its past, converted to harmless metaphor.
In that sense, I think all of this "These people can say it, these people can't" is just a band-aid over a wound. We need to deal with the societal racism that makes people want to cling to the word's potency. That's the message that people like Bill Maher need to hear - that there's a lot of pain in society still that you dredged up by using that word - not this tribalistic "this is our stuff and you can't have it" argument. That only galvanizes shitty conservative opinions that Black people are "snowflakes" who are easily "triggered", etc., etc. And that leads us into an unending cultural tug-o-war with no real goal.
Sorry, kind of rambling. tl;dr I don't know if it's productive to play the "this is ours, not yours" game because 1) language doesn't work that way and 2) it avoids the real issue underlying the word's continued ability to do harm.