In the Vancouver Sun, Peter McKnight argues just that, on the grounds that the aboriginal prison population keeps rising, ‘lighter’ sentences often aren’t, and they provide more opportunity for rehabilitation.
His suggestion that the court system has an institutional bias against aboriginals is silly, but I think this is still a reasonable position. If different groups have different capacities, then they also can’t be held to the same standards. (However, a better solution might be to punish the members of some groups more brutally and with more immediacy in order for the lessons to stick. I’m not sure.)