Doubt and morality: Weighing Moral Codes

Most humans have a sense of right and wrong and would, we hope, try to do the right thing, whatever the situation dictates that particular right thing to be. Immanuel Kant, in his book 'Groundwork for the Metaphysics of Morals' outlines the socially normative underpinning of ethical behavior and shares with the reader his categorical imperative, which states that we should act in such a way that that action could be made into a universal maxim.

Immanuel Kant 1724-1804, was a German idealist philosopher
who wrote about ethics, metaphysics and perception,
among much else. He is often considered a central thinker
influencing much modern philosophical thought.

In other words, act in a way so that your behavior can be emulated by any other person with no harm to them or others.
And, by the very lights of his own theory, we could apply Kant's categorical imperative as the only moral code the human race ever needs. But we know that various cultures and ideologies have varying moral codes and the critical skeptic has got to wade through these in order to measure their efficacy. We cannot afford to take certain moral codes at face value, any more than we can any other idea we may be faced with. The ideology of doubt demands that we carry our tools of the critical faculty with us into the many different versions of what is actually right and wrong.
The reason that we must be willing to do this, is because, once again, human credulity often leads people into unethical behavior, which, unbeknownst to them, can be harmful for everyone. The critical skeptic must carry with them a sense of what is truly ethical and moral in order to weigh the other proffered moral codes against. The categorical imperative is an excellent standard by which to make this judgement.
There are a few general rules that one can ask that help to discern whether or not a moral code is really what it claims to be.
First, we can ask who benefits. If it is not the person or their immediate family group, then it is probably not a good code.
We also need to ask what the source of the code is. Is it applicable to our day and age? Does it take into consideration current scientific understanding? If not, once again, this is not the code for you.
Finally we need to think about whether the moral code in question would indeed do well as a universal maxim. If this became the morality of every single human on earth, would the world become a better, or worse place?
Dealing with the myriad moral codes in these ways give us the ability to decide which are actually beneficial to humanity as a whole.
The critical skeptic has a moral obligation to point out immoral and unethical codes and laws even more than we have the responsibility to point out bad ideas.