It's the most simplistic and weakest sort of argument to make - the slippery slope.
If we allow people to do x, then it's only a matter of time before they will do y.
In this case, if we legalise gay sex, then it's only a matter of time before we legalise bestiality.
It's like outlawing slavery, or giving women the vote, or allowing inter-racial marriage. Such things were illegal because there were those who feared that allowing them would be the beginning of the end of civilization.
It's the most simplistic and weakest sort of argument to make - the slippery slope.
If we allow people to do x, then it's only a matter of time before they will do y.
In this case, if we legalise gay sex, then it's only a matter of time before we legalise bestiality.
It's like outlawing slavery, or giving women the vote, or allowing inter-racial marriage. Such things were illegal because there were those who feared that allowing them would be the beginning of the end of civilization.