I've encountered a sentiment up close a couple times to make me wonder if it is a 'thing'. First time was with a roommate, the white straight male one. He was talking about the future, his concerns about the future with his then girlfriend (now wife). He liked the neighborhood we were in, but had some concerns about living here with her. He had very strong concerns about her safety, about her walking on the streets alone, afraid she'd be raped or something. They wound up in another part of DC, with (as far as I'm concerned) the same crime issues, but much hipper and a better selection of retail and restaurant options. At the time, I was in 'strong independent woman' mode. I was slightly offended of the idea of woman as weak thing that without man at her side will constantly be at the mercy of the criminal element.
The second was with my own husband, the Help. Now the Help and I had been platonic friends for about a decade, so we had a relationship before amor came in. After marriage I noticed he was trying to take on more of the protector role, to which the 'strong independent woman' that was me responded with, "what the Hell?" In an animated discussion about my safety, he expressed concern (despite my years of being safe when the neighborhood was more dangerous) and I countered with asking about the safety of a single female neighbor. He responded that the neighbor I mentioned was not his wife.
In the two examples, the males were white and the females, black. I've heard similar sentiment from other white guys regarding their live in girlfriends and wives, where the guy was white. And from some women inquiring about moving to the neighborhood, hinting that they can't be safe without a guy (bf or husband).
My own father, a black man, never seemed to take on this role. It wasn't protection but honor and respect, where his interests. Other black women seemed to take on protection, in a motherly fashion. There are issues of manhood and masculinity in the Black community that I really can't address here, so I won't.
After marriage, I'm letting go of parts of the 'strong independent woman' and submitting (as I've decided to interpret it) to my husband. I've grown too attached to my husband to think of living independently without him. I allow him to drive me to work, so he can protect me from the bus ride I'll have to take after work. I allow him to be concerned about aspects of my safety that are much in his thoughts, while I continue to maintain and strengthen those areas of our safety that have not crossed his mind.