A mother asks her son "what's up with your sister?". Son: she's on her period. Mom: why do you say that?. Son: because grandpa's dick tasted like blood.
That is gross. What are you trying to say by this?
It was just a joke about how she gets used by her grandpa.
Jokes are supposed to be enjoyed but all, but joking about somebody being raped by their grandpa is mean. If you were raped, you wouldn't want people to joke about it.
You need to lighten up.
You need to understand how hurtful these things can be. People do not like their traumas being joked about, it is insensitive.