The group isn't preventing white people from coding. If you want white people to code, you can make your own group. And it will fly really well anywhere in the South and many places in the West and you won't have to say anything about how it's only for white people, there are a hundred ways that can be signaled.
Again, if you want to help boys specifically - I actually think that's an important target for 'affirmative action' because boys are falling so far behind in academic achievement. Do it. Good for you.
And good for the people trying to help black girls