I eat a nearly entirely plant-based diet and ride a leather B17 Brooks. For me, a stretched leather saddle is a saddle and everything else is a seat; the level of comfort, especially when the ride goes over ten miles, simply can't be compared. My bum may get sore but nothing goes numb; this matters.

We all have our reasons for eating and buying as we do, and I'm sure you can find something that fits your ethics and works for you. For me, a leather saddle, made by skilled industrialized workers paid a fair wage, that protects my arse and will last a lifetime, is worth a bit of compromise. It bothers me less than the metric tons of blood, bone, and feathers that are dumped on the soil used to grow my organic vegetables, which I'm also reasonably at peace with.

I personally know three other Brooks owning vegans; it's a bit of a trope. :-) Your mileage may vary!