At least so says Skeptical Vegan in Homeopathy, Unethical Quackery. I see vegans peddling alotta bullshit so I might challenge his final assertion:
All I have left to say is in my book homeopathy isn’t vegan, it’s 100% bull crap!
Still, since vegans fret over homeopathetical amounts of isinglass they might similarly be concerned about the duck’s liver in Oscillococcinum. You would ingest more molecules of animal products just walking by a McDonalds though. There’s also lactose base in most tablets and animal testing involved. Perhaps an appeal of animal ingredients or animal testing is what it takes for vegans to shun homeopathy but I think a general sense of reason is all it takes.