Whatever the reasons are, it is a socio-economic problem, it's not a problem caused by any form of systematic discrimination in silicon valley.
I do not believe that I have ever seen any youtube video of a black person complaining about how he is fighting to get a job in silicon valley, but nobody is hiring him, even though he has a great number of projects online and everyone agrees his code is great.
It IS a meritocracy. If you put a bunch of bad black programmers in silicon valley and expect them to learn the tools on the job, then this will be an even greater disservice to the black community - as it would result in a negative stereotype about the quality of 'black programming'.