I think it's partially a function of how common and brutal is the deed. You can rip people into pieces in game for a family entertainment because it almost never happens anymore. Sexual violence still happens way too often so its nastiness is more real for people.

Also sex is generally taboo way more than just murder. Soldier killin people - good. Even innocent women if it's indirect enough like bombing. Soldier raping people? Oh, no, we can't have that!

Also not all murder is equally safe for entertainment. Chopping enemies on the battlefield - great. Stalking innocent people in the city to murder them... Way more on the edge of what's acceptable. Even gunning down civilians in the airport raised some eyebrows.

As I'm getting older I'm getting softer. Recently I was sad because I unintentionally squashed Jeff in Half-Life Alyx, blind mutant that was pretty much helpless if you were careful about the sounds you make. Game characters cheering totally didn't sit well with me.