These jokes aren't funny. They marginalize an entire nation of people. You should stop making them.
That's absurd. 419/Yahoo-Yahoo and corruption are a big problem there. That makes Nigeria poorer, not jokes.
If that's true, how about you simply make your comment minus the joke?
Also worth noting that those scams mostly come from the United States now, not Nigeria.
http://www.sfgate.com/crime/article/U-S-Internet-fraud-at-al...
http://www.economist.com/blogs/economist-explains/2013/05/ec...
People are too sensitive these days. Especially people who get self-righteously offended on behalf of someone else.
Relevant: http://www.huffingtonpost.com/2014/12/01/chris-rock-colleges...
I am Nigerian. Not that it matters.