I don't buy the slippery slope argument. Ever. It's fallacious lazy reasoning. If they introduce bad policy, oppose it when it's bad policy. Not when it's a good policy that might later become bad policy if it's changed.
That's not the same, fwiw, as opposing bad policy that's bad now and also has the potential to be extended to be worse policy in the future. Which is where I honestly think you're sitting with this here, based on your other comments. But if that's the case, don't hide behind a comment like this one that entirely rests on "it could be bad in the future".