You wouldn't expect that you could get in much trouble for mispronouncing the name of a river. I've done it myself. For example, when I was a little kid, I did a lot of reading, and I guessed that the name of the river floing through London should rhyme with 'Ames,' Iowa. No such luck. The 'Thames' is pronounced 'temz.' Go figure.
Now, the Niger is the third largest river in Africa. It follows a boomerang course, flowing north, then east, then south, through Niger, then Nigeria. Back in 1972, Joseph A. Walker wrote a play entitled 'The River Niger,' which won an Obie as the top Broaday show of the year, and later a movie starring Cicely Tyson, and James Earl Jones. One day, my dear ol' mother, may she reast in peace, asked me about that play. Apparently she'd read about it, but had not heard anyone else discuss it. And Mom mispronounced the name of the river. Uh-oh! I was totally aghast. I said, 'Mom, it is called 'The River NIGER!' That's Niger! With ONE G! NI-GER! NOT the way you were pronouncing it!' "Are you sure?" 'Yes, Mom, I am sure! I am totally, 100% sure! Trust me on this one- it's 'Niger'!' I am SO glad I managed to make that correction before dear ol' mom committed a major gaffe.
P.S. All things considered, I'm grateful for the fact that my mother never met the activist, Niger Innis.