The severed heads didn't bother me, btw. The Klingons are supposed to be extreme and even gross on occasion: they eat live worms, they drink "bloodwine," they like rough sex, they batter each other with pain-sticks, they have mind-rippers and vicious monster-dogs, etc. Severed heads are at most a difference in degree not of kind. Shocking is kinda the Klingon's thing.
And, honestly, a couple of severed heads is pretty tame by modern standards. Forget GAME OF THRONES; severed heads are a staple of Halloween horror decorations, old Vincent Price movies, etc. I get that not every Trekkie is also a horror buff, but a severed head or two are not exactly beyond the pale and haven't been for decades. You had severed heads on DARK SHADOWS back in the sixties, and that was on daytime TV.