The problem is that it's a lot harder to execute -- if you have a "Kids Code" event, you are
guaranteed to get a disproportionately larger number of white males.
This isn't just about helping a disadvantaged group, but also signalling to them at a young age that "people like you are also programmers!"
Growing up as a minority is something that is difficult to grasp unless you are part of that group -- something as simple as having fewer role models who look like you can impact your choices and decisions to pursue specific careers.
And no, they are not refusing to help males. I'm almost 100% sure that if a male asked if he could have some help learning to code, someone would either help him out or point him in a direction where he could get help. The group is just designed in a way to signal to young girls that they should join and learn how to program when pop culture ordinarily defaults to making scientists males (e.g. Big Bang Theory).
EDIT:
Here's another question: is it wrong for a church to provide support groups for its members? Is that discriminating against other religions? Or is it just an effort to improve a specific community?