We can only behave according to what is acceptable in the present moment we happen to exist in, it would be unreasonable to ask people to attempt to predict fut

We can only behave according to what is acceptable in the present moment we happen to exist in, it would be unreasonable to ask people to attempt to predict future morality when making ethical choices. We can try to make a good guess about it and act accordingly but it'll never be perfect, nobody can make a ruler with units that don't exist yet let alone try to measure something with it. I think intent counts in these situations too, like you say Monty Python never set out to be unkind or bigoted to anyone. Would it be an acceptable sketch today? Probably not, and that's not really a bad thing given that improvements to the rights and recognition of transgender people is one of the more positive things to come out of the last couple of decades in my opinion. Should Monty Python be cancelled over this sketch though? Not in a million years.