because, as I see it, Vin Diesel - a man, is part of group which enjoys a certain privilege or dominance, and a set of experiences, which women do not. so, if you call him a dickhead or what have you, the connotations are not the same as calling a woman a "fake lipped bitch" - putting her down in a number of ways, including her appearance. similarly, Madonna gets criticised for her looks / clothes, but men of a similar and even higher age do not.
it's like when a few times, some old white men (you know, "good ol' boys") in the US talked down to me (another caucasian, if 'foreign', person) and called me "boy" - yeah it was somewhat unpleasant / condescending, but not even remotely comparable to an instance if such a remark was directed at an African American person.
but I'm sure that you know that b/c you're an intelligent person and I think you are above this reddit-esque reaction (where posters scream "but look at all the misandry WE experience!" whenever they are pulled up for making sexist remarks).
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a separate issue is people disliking LDR's music - a sentiment I understand, but do not share. dunno, I have a pretty narrow / shallow knowledge of music and I'm sure there's music that is much better out there, but I really, really like the album.