I am looking at this from the perspective of a deontologist, who is against the hedonistic utilitarian theory of John Stuart Mill. John Stuart Mill's version of the hedonistic utilitarian theory does not take motive into account when determining the moral worth of an action.
So far, I have the following argument as to why motive should play a part in determining the moral worthiness of an action:
Believing that motive has no role to play in the assessment of a moral action, this means that, as humans are apt to make mistakes, if we do the wrong thing by accident, we are considered morally wrong, even if we have noble motives. Furthermore, if we have sinister reasons for doing something, and we do the right thing by mistake, our action is still considered morally right.
Does anyone have any other ideas as to why motive should play a role in determining the ethical value of an action?