Yeast are fungi, so not really an issue.
So they are kingdomists, is that it? All the rights to the animals, no matter how lacking in sentience they may be, but none to the other kingdoms.
I get animal welfare, I really do - or at least I think I do - and I'm very concerned about it myself, especially when it comes to animals we use for food; but my concerns are usually reserved for creatures that I view as actually capable of suffering in a meaningful way. Not to mention that I disagree with the notion that the bees in honey production are abused. After all, the beekeepers want their colonies to thrive and therefore usually only take a part of the honey they produced, while replacing it with other consumables for the bees to use instead. One could
argue that this is a symbiotic setup, with humans providing shelter, plenty of flowers nearby, protecting from frost, storms, forest fires etc.; of course, one could also make that argument with regards to other animals we use for food (how much success would a milk cow have in the wild, really), although I'd argue that those situations involve beings way more capable of suffering under the provided conditions.