To be fair to OP, the point someone made about injecting toxins could have made the same point by saying poison instead, and then it would have been harder to argue with OP's response to it. In conversation it's not that weird to think of poison and toxin as meaning basically the same thing, even if it's technically incorrect, and it's pretty much a truism that effective drugs have risks and "the dose makes the poison" (kinda — it does get more complicated than anything Paracelsus knew about). OP had already made her decision on the Botox part, so I guess she's not put off by the fact it's dangerous at higher doses.
I get why the disclaimer might've taken you unawares and you felt reluctant to just accept on the spot, OP — presumably you spent time thinking about whether the Botox risks you knew about were worth the benefit, and decided it was worth it, but then you were handed this form to sign with info you hadn't known, and didn't have a lot of time to assess and incorporate this new factor.
Also, if you're around my age you probably grew up being repeatedly, heavy-handedly instructed on the dangers of blood-borne or sexually-transmitted incurable diseases, with messages from school, media and government designed to put the fear of God (or at least, of drugs and sex) into you, followed by various news stories about epidemics, contaminated blood products, and that sort of thing. It's understandable to me if the disclaimer pushed some of those buttons for you. It's okay, I think, to want to give yourself enough time to work out what that disclaimer means in practice, maybe check the safeguards, safety record and alternatives, and reassure yourself that it doesn't significantly change the risks involved.