Cradle of Filth haven't really been true black metal since the mid nineties when they sold out for the first time by concentrating completely on fantasy horror lyrics rather than paganism/nationalism/anti-christianity after a tabloid scandal in which an extremely devoted fan of theirs desecrated a number of churches. They were always a bit black/death hybrid anyway, and from the first they've constantly evolved into a broader mix of metal styles that now, I have to say, owes far more to commercial considerations than any artistic convictions. The real reason that black metal fans tend to denounce all Cradle of Filth, however, is that they have never been entirely serious. I still like a lot of Cradle before the more dire recent albums simply because they're so much fun. Tr00 Black Metallers, even if they can't pin it down exactly, hate the percieved idea that a band MAY NOT BE TAKING THINGS SERIOUSLY. It's one of the reasons Carpathian Forest don't get nratly as much respect as they deserve whilst Darkthrone, though they are admittedly quite good, get somewhat overhyped.
And some people do just hate Dani's voice, though my favourite comment on the whole thing is contained in a cartoon printed in the back of an early issue of Zero Tolerance, the site for which annoyingly down.
First Frame caption is "Cradle of Filth are always the subject of drastically differing critical viewpoints. There are those who like them..." and then in the first frame a smiling metalhead giving a thumbs up and saying "Dani is the very essence of Masculinity!" Next frame, "There are those who don't..." and a grim black metaller frowning and saying "The only TRUE black metal band was formed before Time by the Aryan demon-father of Satan in the deepest caverns of Hell, recorded onto the genitalia of mutilated christian virgins and can only be heard by the corpses of long-dead pagan demigods!" and in the final frame the caption "...and those who really, really don't", with a picture of a distressed looking priest screaming "SATAN IS IN MY EARS".