Well, this is disturbing... Bing's ML image generator will generate male politician video game character portraits no problem, but change the word "male" to "female" and it gives a content warning and blocks the request.
Interesting. If I do not specify the age/race of the character to be generated, it then allows it. I removed the terms "caucasian" and "middle-aged" to get past the block.
Okay, I think I found the formula. If you include any racial indicators (i.e. "African American", "Caucasian", "Latino") and you include the word "Female", it blocks the request.
How bizarre.
But it does allow more descriptive terms, like "dark-skinned"...