the slippery slope came up in the 60s when the SCOTUS was hearing Loving v Virginia, the seminal case on interracial marriage.

people argued that once interracial marriage is normalized...

then comes normalizing homosexuality.

then comes normalizing transexuality.

then comes normalizing pedophilia. <= you are here

then comes normalizing bestiality.

then comes normalizing necrophilia.

then comes normalizing gangrape.