Sadly, the offensiveness of terms such as tar-baby lies with the beholder. You use the word in one context, you use it correctly - but the less skilled user of language misunderstands (or chooses to); I suggest it falls in the same category as the golliwog; no longer acceptable in this PC world (which is why I prefer Apples).

How could niggardly be offensive? The etymology has nothing to do with negroes and to jump to conclusions of racism implies a sad failure of vocabulary. In some environments this misunderstanding might form an accetable pun. Would that we all lived in such circumstances.