Now you're assuming what the actual design of the pin and mask were... Do you know it was just "BLM"... and why wouldn't that count as a brand/logo? Just because it's not trademarked it's not a logo? That's silly and certainly not a consideration for what is and isn't a logo. There are many masks and pins that are absolutely stylized. But I have no idea which these people were wearing so I won't speak to that.
LOL <- do you think that’s a logo too?
LOL can be a logo. But I find myself again pointing to the rules that Whole Foods have in place...
You must wear plain tshirts (no pattern or multiple colors, only plaid) pants must be one color and in good shape (no holes) you can wear shorts in grocery and front end and produce but must wear pants in prep foods. Close toed shoes. Hats must only be whole foods logo and if u wear leggings you have to wear a shirt that is long to cover the butt. No pins on your apron and no logos or sports teams or bands.
"plain", "one color", and NO pins... These things are obvious and clear words that don't leave imagination to the intention of management. Even if it was just the letters BLM put together in a neutral font... it's still a violation of the contract you would have agreed to in order to work there. If you have no intention of following the rules, then don't work there... and certainly don't "surprise pikachu" when you get fired.
But even to just the point of what a logo is...
https://www.merriam-webster.com/dictionary/logo
2: an identifying symbol (as for use in advertising) 3: an identifying statement : motto
We could argue that BLM meets or doesn't meet requirement for definition 2... But it DEFINITELY meets definition 3. BLM just on it's own is 1 of 2 things... Bureau of Land Management, or "Black Lives Matter" (whether the non-profit or the movement). It's definitely identifying because nobody is wearing a Bureau of Land Management mask or pin.