He use a correct word for the situation, the word is not related to the word nigger, though someone unfamiliar with the word "niggardly" might take offense due to the superficial phonetic similarity between the words. Did the guy make an error, partly, you only use the words your audience will know, he was not wrong for using the word, just for using it with people who don’t know it.
I use the saying 'pro bono' a lot, to do a service for free for the public good, as some of you know I do computer repair for a living, and for college students, I cut my rates, sometimes I do it for free, (specially when they are cute
) but on several occasions, the person I am talking with don’t know the word, and I get slapped, (pro bonner), one nice gentleman said 'I’m flattered, but I don’t swing that way'. Is using pro bono also wrong? No, it just has to be used with people who know its meaning. After these incidents I explained the saying, and everything is cool, that is what this David Howard should have done, noticed some one took offence, and quashed it then and there, apologies and explained the word has no relation to the n word, and given its definition.