It has definitely been a rapid transformation. I remember being at the beach in the early 90s, in those big souvenir stores that are on every corner, and all the "suggestive" t-shirts were a subject of great amusement to my 14 year old self. But in particular I remember one shirt that was a take off on the Trix cereal rabbit. It said "Silly Faggot, Dicks are for Chicks". Yes, crude and hardly something to wear in polite company. But the point is, that was representative of attitudes at the time. It was considered crude humor, but not some great horrific -ism that demanded an immediate candle light vigil.
By the end of that decade the same t-shirt would bring out full blown apoplexy. It's a rapid transformation, so rapid that it is clearly an engineered one.