That so called compass is completely relative, as other atheist here have already confirmed.
It's the exact same compass as you have. Because we are both human.
And it's not that relative.
It's, at bottom, driven by empathy and, on top, influenced by culture.
More importantly, moral judgements are like logical arguments.
You have a few premises and a conclusion follows.
But like with any argument, your conclusion is only as good as your premises.
So knowledge informs morality.
Deeper and better understanding of human nature, human biology, etc informed us that the practice of slavery was morally indefensible. Today it's illegal in most of the world except a few hellholes
Deeper and better understanding about animal well being informed us that torturing them (in experiments, in games, whatever) is morally indefensible. Today we have things like animal rights.
So this is how morality develops. It's also how it differs from culture to culture.
For example, a culture that imposes premises like "god thinks homosexuality is evil", those people will be concluding that it's evil.
The problem is not the logic of the argument. The problem is the premise. It's unsupported nonsense.
When you only use supportable premises, you actually can't come to the conclusion that it is evil.
It's also situational.
What is bad in one context may be the right thing to do in another context.
To me, morality is pretty objective.
I am of the opinion that there is such a thing as objective morality.
Morality ultimately pertains to well-being.
So, ultimately, whenever we make moral judgements, what we actually look for to determine the "severity" of the act, we look at what the impact of the act was on general well-being.
The greater the cost to well-being (in all its aspects) the more "horrific" the act will be and thus the more "evil".
This means that on principle, the well-being cost of any act can be objectively determined.
Ironically, this entire exercise ceases to be objective, once we throw out the rule that premises must be supported by objective evidence.
If one is going to inject premises from some faith based religious beliefs....Obviously we are no longer being objective.