Joe, the reason why I distrust conscience is that many people use it as their reason for choices of behaviour, decision-making and actions, when it simply means it's what they wish to do.
Feeling something is 'right' according to one's conscience doesn't make it so.
I've always felt that society's ethics and codes of behaviour are liable to be dodgy and not 'self-evidently' the best way forward. But that's only my view, and it's just as dodgy as anyone else's.

However, I accept that in travelling through life, one has to apply some sort of rule/code for oneself. This is where such words as tolerance, kindness, compassion, empathy, honesty, fidelity, support in trouble, altruism, courage and so on come into play.

But actually, even these sterling qualities can be misguided and inapplicable to certain situations.

Tolerance - towards paedophiles, domestic abusers, Jihadi?
Courage - risking one's life when one has a family at home to support?
Compassion - for prisoners who have mugged the elderly or stabbed a youth in a drug feud?
Non-violence - if a burglar enters one's house and assaults one's children?
I suppose I could sum all this up as 'Nothing is certain and nothing is self-evidently right or true'.