I think the less GLs interfere with lodges, the better.
Each lodge should be able to regulate itself according to the Const. and landmarks. No lodge should be compelled to take a candidate. There is no rule that all petitioners should be accepted. Trying to prove discrimination on race is tricky, and on one level, all are discriminated against, male, over 18 (or21), not an atheist etc... I would NEVER propose a candidate who I thought would be blackballed. If a lodge would not take a worthy candidate because of the colour of his skin, I would keep searching until I found a lodge which would. Fortunately, I am not a member of a lodge like that, nor do I know one in our Const.
Here is the criteria I use, once all the standard stuff is ticked, the question comes "is this a guy you would want to be at a dinner party with ? is this a guy you would like to spend a weekend with ?" At the end of the day, lodges are social places and need to be built with that in mind breeding out unfavourble characteristics (racism being one) and creating a body of men who mutually support and improve each other. That's not about rules. That's about creating culture.