The “authorities” aren’t “in the pocket of politicians.” But we have seen all over the developed world that they’re human, and not neutral, and suffer from their own ideological biases. Moreover, the “fact checkers” tend to come from the same social and economic class, which heightens their biases.
Again, then this law is totally harmless: if indeed people are biased when they decide if someone lies or not, it does not matter if there is a law on it.
Again: if you are claiming that this law will harm opposition, then you are not saying that "human are not neutral", you are saying that everyone involved in the process are magically all aligned in exactly on side. If there are people biased "in the other direction", then they will be biased to say the accused is innocent, and it cancels out.