When it is selected based on strength of their (hereditary) connection to the Force, then it is not quite speciesism. Because then the primary parameter is not species, but connection strength. When a human apprentice is favored over a non-human apprentice because (s)he is human rather than because (s)he is stronger in the Force, then it is speciesism.

Because most of the non-human species cannot breed with the various human species, then favoring bloodline does not really make sense as excuse for discriminating against certain species, so long as there is a common frequency of strength in that species.

The sole reason, we believe, for the speciesism and female oppression to have been included in the Empire in the first place is that they're nasty evil habits that George Lucas added simply because it would make the Empire less likable. Adding a trait to make something more evil rather than because it fits their morality makes no sense for compiled lore.

There are many ways of interpreting the Sith code, even for interpreting it to mean freedom from [insert rule list/source]. There are Sith that will hurt people because its fun. But you find those traits among all groupings, probably even among Jedi, even if they find some excuse for it. A number of Sith are pretty ruthless. When it comes to achieving their goal, they do not ask "is it acceptable to do this?". They ask instead "Will this do the trick?". That is the sort of independence we meant.

The Jedi on the other hand, tend to stick to extremely strict codes. At many times throughout EU history, its been seen that the Jedi cannot accept anyone deviating from their rules and regulations for using the Force. Like after the defeat of the Sith in the Great Hyperspace War, When the Jedi and the republic actively slaughtered any Red Sith they could find, even the women and children, simply because they did not follow their rules.

Outside certain games, there aren't many force disciplines that are impossible for Sith to use. Yes, there are some that are less likely to be used, but we cannot think of any that a Sith cannot use and remain a Sith. The difference between Sith and so-called "gray" Jedi is more in their reasoning than in their use of the Force. A lot of gray Jedi use the dark Side while telling themselves its for a good reason/cause/whatever. (That sounds a lot like ends-justify-the-means, doesn't it?)