|I know mine looks best when framed in curls, which is natural for me. Dreds or braids would be natural, too.|
My first thought was to find it odd to classify dreadlocks and braids as "natural." As far as I can tell, both involve quite a bit of work (and in the case of dreds, often some application of styling product). While it may not be as much work as the "unnatural" option of straightening black hair, I don't see an obvious cleavage that would lump dreds and braids in with leaving your hair alone.
But I think there are two senses in which dreds and braids could be classified as "natural." One has to do with the motives for choosing a given hairstyle. There is a presumption in the progressive hair politics position that very few black people would consider straightening their hair in the absence of racism (i.e. unnatural exogenous interference) teaching them that curly hair is bad. But racism is much less of an explanation for why black people would choose dreds or braids, since racist whites condemn those styles as much as they condemn minimally-styled black hair. I think it's tricky, however, to presume that any choice is an obvious natural one, particularly if it involves a significant investment of time and effort (as putting in braids or dreadlocks does).
The other way that dreds and braids can be considered "natural" is by focusing not on the style or stylist, but on how the hair is read by others. A big part of racism is casting the oppressed race as more "natural" in a pejorative sense. Racism holds that black people are less civilized, more prone to undisciplined passions and a failure to take responsibility. Dreadlocks and braids are distinctively black hairstyles, and are thus by association more "natural." Straightened hair, on the other hand, is "civilized" (or "professional," professionalism being the ultimate expression of unnatural-in-a-good-way) because it resembles the white-based beauty standard. What's more, the various hairstyles are taken to connote something about the person who has them. A black person with un-straightened hair is taken as someone less willing to play along with society's demands. From a racist perspective, not playing along is generalized into being dangerous, unpredictable, and immoral -- hence "unnatural" and animal-like**.
*When I was younger, my hair was literally white, i.e. it lacked color. It darkened over time, and last year when I got my new Arizona driver's license, I was officially listed as having "brown" hair.
**Though as Mary Midgely has pointed out, the kind of undisciplined human behavior usually condemned as animal-like rarely has anything to do with the way real animals act.