If we can find an alternative, like using computer models, it'll be good. But for now computer models can't replace animal experiments, yet (sadly). Like some follow-ups pointed out, this kind of accusation should not go too far, otherwise, similar accusation applies too all who eat living things, including plants. Yes, I know, this is a far-fetch counter-example. Then back to the starting point: the protester should act more constructively, like proposing an alternative for animal experiments. (unless they would go that far to propose thorough prohibition of medical experiments).