I can confidently say that I personally saw a sea otter about 15 miles north of Santa Barbara about 5 months ago that was snacking on purple sea urchins. It would go down, come up, do something, and repeat, and I came across several very-recently-eaten purple urchins washed up along the beach on my walk that morning.

I also pretty regularly collect urchins in that kelp forest, purple and red in that area, and the ones the otter were taking were smaller than the ones I would have chosen. So, at the least, there's at least one sea otter that particularly cares to each some sea urchins, and one human that cares to each the others.