I dont fully agree with ozpin as a murderer as it forgets a BIG thing.
Salem will kill everyone. That is her goal to remake the world in her image.
So having people fight Salem in no way makes him a murderer because he isnt trying to kill them at all he is just trying to stop a world level threat that is Salem.
Salem WILL kill everyone Ozpin is trying to stop it. Him doing that in no shape or form makes him a murderer.
As for your point on Leonheart and Qrow that is actually the point he cant. People change with time as Leonhart was specifically said to be a strong warrior which is a far cry from how we saw him time and experience broke Leonheart.
And as Ozpin flat out says Leonheart is not the first and the words Yang gave him are stuff he heard from leonheart as an example.
So no he really cant trust completely because of the weight of all the things he has to juggle.
Ozpin is not out of ideas he cant kill Salem so he is clearly working on the otherside of the equation bettering humans and Faunus so he can call back the gods who CAN kill Salem. We see this he pushes for equality in Human Faunus relations.
People are so focused on the idea that Ozpin did something wrong they forget a lot of the situation that heavily dictates his responses and behavior. Salem is an unkillable demi-goddess who has engines of Murder and destruction at her beck and call, which her goal is to become the new god of the world and remake it as she sees fit.
He has magical artifacts to help him but they are a double edge sword as anyone can use them and they have a limit. Oh and if they are all gathered in one place end times get started.
Ozpin is reacting and trying to predict and cut off Salem while working towards what is a thin and unlikely goal he was given by the god of light. That means he makes mistakes and big ones at that but its not him trying to hurt anyone actually the opposite.
People need to stop trying to confront him and actually trying to understand him. Because that giant blow up from the girls? Its pretty clear that is what happens NORMALLY when he tries to tell people.