"Ok but what makes a thing immoral if not humans judging it immoral?"
The effect on the net well being of those toward whom the thing is acting.
"What non subjective standard is at work here?"
The measurable effects on the well being.
"It is not generally considered immoral to harm a human (or a non huuman) accidentally."
That's because intending for the maintenance of well being isn't immoral.
"A crocodile is rarely judged as immoral even when it does great harm to humans (or non humans)."
Crocodiles make moral decisions too, and if it's the case the crocodile could have maintained more well being by not consuming the human, then it would be immoral, if it's the case that the only way for more well being to be maintained was for the crocodile to eat the human, then it would be moral.
A volcano is even less often judged by this standard. Doesn't that sound like a subjective standard to you?
Well, the volcanoes can't make a decision between what activity would bring about the greater maintenance of well being, so whether or not its "behavior" can be considered moral is in't indicative of whether or not the volcano is actually behaving towards others.
"If harm were an objective standard unintentionally harming humans (or non humans) would be immoral."
Except that intending to maintain well being is moral.
If we learn that particular actions, though well intended, are harming the well being of others, then when one intends to behave towards others and doesn't consider this fact, one would be behaving immorally.
Truly intending, with the best of your knowledge and ability, to maintain well being is moral, and learning about actions that impede this end is moral, because it serves to avoid that recently realized detriment to potential well being for the future.
"and if intention is a part of our standard then crocodiles harming humans (or nonhumans) would be immoral"
It depends if there were other options of greater well being.
See above.