CJB5252, when a single court gives different sentences for what appears to be the same charge, it's usually for a reason.  I can't imagine for a minute that the lawyers for Lovelace and Sherman wouldn't have mentioned it if the sentences were racially-based as you say.  

Keep in mind the punishment was for flagrant refusal to obey a court injunction.  I say flagrant, because both Lovelace and Sherman said, in court, that they would not obey the injunction in the future, either.

It appears there were other first nations protesters subject to the injunction, (from the Shabot Obaadjiwan First Nation) who were not given any sentence, because they had agreed to obey the injunction.

I tend to think there's something your white friend didn't understand about what happened.