idk if theres easily digestible youtube video essay type content out there talking about why eugenics is bad. maybe you could show them a phrenology skull or eugenicist literature https://rarehistoricalphotos.com/vaughts-phrenology-book/ but i feel like you could probably just use the socratic method, ask questions, and see where you end up. like:

• "why do you think this is a good idea?"
• "what happens to people who you want to remove from the gene pool?"

maybe that could be a good point for you to link it back to genetics and the evolutionary advantage of genetic diversity https://kids.frontiersin.org/articles/10.3389/frym.2021.656168 if theyre trying to portray this as though its for the benefit of the human race

• if you believe in sterilising undesirables, who will do the sterilising? if you believe in killing undesirables, who will do the killing?
• who will classify people as undesirables?
• if people are classified as undesirables based on supposedly objective measures, who developed these objective measures? how do you know that they're objective? if this is based on criminal conviction, how do you know the courts have ruled correctly and fairly?
• what happens when a non-undesirable person is misidentified as an undesirable? is that a tragedy?
• do you think that undesirable behaviour is the result of nature or nurture? is undesirable behaviour the genetic destiny of undesirable genes?
• what happens when The Party That You Don't Like comes into power over this program?
• is this program democratically controlled? would democratic control of this program be a good thing? how else should it be controlled?
• are you an undesirable? could you become an undesirable?
• how do you feel about the way eugenics has gone in the past (i.e. a justification for imperialism and mass death)? what will be different about your ideal program?