"are all vegans / buddhists anti abortion then? (serious question)"
The Dali Lama says that it must be viewed on each individual circumstance. It is generally considered the a abortion has moral and karmic consequences. Compassion for the Woman is the guiding principle on this, then it is a personal matter.
Veganism is about not practising speciesism. Abortion is generally considered a personal matter, again Compassion and respect is the guide.
You get extremists in all things, though, that lose sight of having to operate in the real, complex World.