The argument is that breeding more animals for the enjoyment of humans is bad, but the existing animals should be given as good of a life as we can. Since rescuing does not directly support the breeders, some vegans are OK with rescuing to give these animals a better life. Some vegans use similar logic to thrift wool sweaters for yarn, when they would not support buying new wool.
So long as the roads are plowed, winter cycling is pretty easy. I bike all year round in toronto, and just the exercise keeps me warm enough that I’m out in a sweater until -10 or so, and any colder you can bundle up pretty effectively.