Haha, I personally don't subscribe to the logic (or lack thereof) behind it, as I consume meat/dairy, wear leather shoes+belts, use goose down jackets+bedding, use devices and appliances powered by electricity produced through methods that can harm animals (e.g. hydro-electric dams, wind turbines), and eat fruit/veg/grains - all things that are farmed and harvested in ways that result in rodents/other small mammals/birds/reptiles being killed as 'pests'...and of course, use a best badger brush. I just observed that an added bonus of using a synthetic brush over a badger brush (aside from the latherability, drying time etc) is that vegans aren't upset by it and I don't have to explain how badger brush knots come from China where the badger isn't a protected species like it is here, is a pest, and is consumed for meat with the hair being a by-product of pest control and meat production, so it isn't just a case of an animal being killed purely for the sake of our shaves. The fewer of those conversations I need to have with (nice, well-meaning but slightly misinformed) people, the better
Of course, if a badger brush happened to perform significantly better than a synthetic (as was the case many years ago), I would have no objection to using one and displaying one on my shaving brush stand regardless of vegan preaching