It's a very common argument, so I can hardly claim it as my own, but a quick search on DDG or your favorite alternative will turn up thousands of hits[0]. Clearly it is true that human beings all over the world have braided/matted their hair for a very long time, but that doesn't seem to me to render arguments about its present-day significance moot, given that many students seem to be expelled for wearing them[1]. Similar results for dread-wearers being fired[2], again, nearly all of whom seem to be people of color.
I don't think a duckduckgo query is a fairly representative study of dreadlocks in cultural significance. A search engine will also turn up thousands of hits for "do vaccines cause autism", lots of which will say "yes".
> A search engine will also turn up thousands of hits for "do vaccines cause autism", lots of which will say "yes".
The fear that vaccines cause autism is culturally significant though. It's so culturally significant that it's causing real damage to society here and now.
0: https://duckduckgo.com/?q=dreadlocks+cultural+appropriation
1: https://duckduckgo.com/?q=dreadlocks+expelled
2: https://duckduckgo.com/?q=dreadlocks+fired