For what it's worth, I am white, English and sing and play blues. I think what I do is just as valid as some middle class people who want to sing sea shanties or songs about farming or fighting in a famous battle.
Blues isn't just a matter of skin colour; in my opinion, it is about a feeling and a love of the genre. A bit of trivia, I sing all my songs in a Scouse accent, which is my "normal" accent.
Now stop fighting.
Love & peace,

Ron.