My take: you get paid to talk on TV. There are some things you shouldn’t say. Certain curse words and racial slurs would be among them. If a newscaster lets go a f*** on the air, there will be repercussions, whether it was intentional or not. This newscaster most likely accidentally uttered the word 'coon' while on air. I think we all could agree that it would be among the words that shouldn't be spoken. Now, combine that with the fact that he was actively talking about Martin Luther King Jr. at the moment he said that word, and the problem becomes compounded. Even the simplest of posters on here could agree that it's a bad moment. The news station should have perhaps reassigned the guy to an off-screen position for a while, but it is well within their rights to look at this situation and just move on without him to protect their station and its profitability. Because we all know what would have happened if they didn't fire him.
If you can honestly look at this situation and think 'no harm, no foul' and get outraged that the man was fired, then I don't know what to tell you. It's truly very simple.