[unix-dude]

I don't believe the author meant that people should be suspicious of "Nigerians" in general, but rather that they should be suspicious of Nigerians when in the context of an online monetary transaction.

The sad truth is that a lot of scammers originate from Nigeria. Therefore, it makes sense to be extra cautious when engaging in financial transactions with someone who is in within Nigeria.

I highly doubt the author was implying any sort of racist sentiment.