There are some things where advertisers do just get an opt-out, but Youtube's existing content policies have a blanket prohibition against "harmful health or me

There are some things where advertisers do just get an opt-out, but Youtube's existing content policies have a blanket prohibition against "harmful health or medical claims" with no advertiser choice available. (https://support.google.com/youtube/answer/6162278 https://support.google.com/youtube/answer/6162278, "Harmful or dangerous acts" section)