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.
0: https://duckduckgo.com/?q=dreadlocks+cultural+appropriation
1: https://duckduckgo.com/?q=dreadlocks+expelled
2: https://duckduckgo.com/?q=dreadlocks+fired