Moral arguments work best with boomers in my experience. Whenever someone is hurt by diversity, I point out that boomers deserve it. Some girl got raped? Tell them straight up that her boomer family caused this and its deserved. They created this bed and now their children will have to sleep in it.
You get confused looks, as boomers are VERY bad at taking any blame for anything. Remember they were taught individualism and personal responsibility (a way to ignore all personal blame for problems in a community).
"Oh, she got raped? Her boomer grandparents probably voted for this, so its deserved. They also probably still support diversity, so I have no sympathy for them or their family"

When they say things like "You can never change this", they want it to be a win for them, but you can make it a complete lose for them by agreeing with them and condemning them morally for the permanent & inevitable destruction they've done to both their children and their civilisation. They're evil, selfish, short-thinking, any derogatory term that hits them where it hurts. Calling them things like "traitors" probably wont stick, but framing it as them stabbing their grand children in the back works fine.

Edit: And don't say it to be edgy, or to trigger, or in other ways where you are appealing to them or wanting them to agree with you. Say it in a condescending, condemning, blaming, distancing manner. You don't say it to "convince" them that they're bad. You already made up your mind and you're not interested in their opinion or excuses on this topic. The only thing you give attention to or have time for is them saying "they didn't want it" or "that they never voted for it". Make them reject or deny (Like Peter denied knowing Jesus). Alternatively, listen if they REPENT or REGRET their actions. Those two types of responses can be met with validation, any other response deserves visible contempt or complete /ignore.