You may be misinterpreting that post somewhat. The argument seems not to be that sending stuff to Nigeria is not a good thing, but that it's not strictly accurate to describe it as increasing cycling diversity within the UK itself. It is, however, beneficial for cycling in Nigeria.
Also I'm not sure that sending bikes to Nigeria is working to make cycling in the UK more diverse.
At best it's a well-meaning gesture, but it's not really the same as being a diverse and welcoming group of cyclists.
Cycling is still overwhelmingly white, male and middle class, even in London.