Yeah, this doesn't excuse anything, but as a millennial growing up there was this whole trend of "dark humor" and "anti-jokes." Basically the more fucked up and wrong something was, the funnier it was supposed to be.
That doesn't make it okay, but we were just stupid teenagers. You could say we shoulda known better, but at the time that was just the trend. Like skibidi toilet and other brainrot today. Everyone knew it wasn't serious, that no one could actually mean those jokes.
At least, we thought we did. It seems as we grew up, we diverged into two main groups. Those who realized how those "jokes" could actually be harmful and grew out of it, and those who started taking the jokes more and more seriously until they started meaning it and it became part of their personalities.
I think that's a huge source of disconnect with Gen Z. I don't think they ever had a concept of dark humor. By the time they reached that age, the trend was more towards acceptance and inclusion, social awareness and non-harmful language. The old "sticks and stones" no longer applied.
So to early Gen Z, late Millennials probably looked like sociopaths. Especially since we were already on social media, and some of that immature bullshit is indelibly marked on the internet.
And you can't just tell them "it was just a joke, we didn't mean it, it wasn't serious" because that's such an alien concept to them.