You say "allows for immoral behaviour", but no system of ethics allows for immoral behaviour by definition. What you're presenting are, for a consequentialist,

You say "allows for immoral behaviour", but no system of ethics allows for immoral behaviour by definition. What you're presenting are, for a consequentialist, the choices between two evils: - do I pay taxes or give away to charities? - do I do fraud or let evil AI go on a rampage? - do I sacrifice my children or let the Romans kill us? You can't argue for things that have no positive consequence: the child sacrifice sounds dumb to us because we see the alternatives as independent. If you only consider either/or choices, the number of things you can justify as a consequentialist becomes limited.