Received demand letter from ungated brand to stop selling on Amazon – what are my rights?

I do online arbitrage and I received a demand letter today from one of the brands I purchased to resell on Amazon. Let’s call them BeautyBrand. I purchased about 12 items from BeautyBrand’s website on sale and offered them for sale on existing Amazon ASINs for these products. They are claiming that I am engaging in copyright infringement by using their logo and such to sell these products. I didn’t upload the logo or anything though, all of the listings already existed on Amazon, uploaded by BeautyBrand itself.

Is this a legitimate claim or are they just trying to bluff me? I’d only take about $100 loss if I stopped immediately but I don’t want to be bullied out of selling something completely legally if I don’t have to. I do not plan to resell any of their products in the future but I would like to at least sell the inventory I have.

Has anyone else had an experience like this? Thanks in advance!