I avoid certain shops because I disagree with their practices, and will happily explain to other people which shops and why.
I don't see this as particularly different from avoiding certain sellers for their practices, and telling your friends who have similar values which sellers and why.
Corollary to this is those who have opposing values choosing those sellers and shops by preference due to agreeing with their practices, and telling their friends who have similar values which sellers and shops, and why.
To use a well-worn example, if a shop refused to bake a cake for a gay wedding, a bunch of people would not shop there because they're homophobes, while another bunch would shop there because they're homophobes. The shop should be "allowed" to refuse custom for any reason, including because the owners are homophobes, and hopefully the second group of people is smaller than the first because homophobia is idiotic.
I don't know what the embroidery/transphobia thing is about, but I'm guessing a bunch of people highlighted the seller's views because they viewed them as negative - but at the same time a bunch of people will see them as positive and support the seller by placing orders.
I also don't see why any of this is "cancel culture". It's consumer awareness and the exercise of free expression.