if one actually understands what a slippery slope is
fighting for equal rights and ending discrimination is not a slippery slope.
animals cant enter into contracts and the law considers that animal abused and a victim based on lack of consent
incest was legal, then it wasn't, now some of it is and that took place BEFORE gay marriage and none of the arguments/precedence line up
so this one fails also, it has nothing to do with equal rights for gays
since you just proved you dont know what a slippery slope is ill explain it.
a slippery slope is when one thing directly leads to another using solely the identical principles, things, etc. In this case it would be arguments and precedence. Both of your examples factually fail those requirements.
your filed logic sounds like the racists and bigots of the past
"if we let women vote might as well let my dog vote, if we let minorities be people my horse might as well be a person, if blacks can marry whites we will be marrying monkeys next."
Sorry these mentally retarded and failed arguments were stupid and uneducated then and the same remains true today.
let me know when you have some more that can get destroyed.
so when you said 100% true if you meant everything after that you were 100% wrong.