I dont get all this rage...first off because they are iconic abilities doesnt make them "Exclusive" iconic abilities. Easiest example, Palpatine shooting lightning from his fingers in the movies. An iconic image but was he the only one ever who could do it? No, and if you read some novels there are even some Jedi that have done it (including Luke at in one novel).
Next...just because your force sensitive, doesnt mean you become a Jedi or a Sith. Perhaps you dont get discovered, perhaps neither faction appeals and you strike out on your own...perhaps you just want to be say...a bounty hunter rather then devote yourself to the simplistic lifestyle of the Jedi.
There are countless examples of characters that dont fit into the "generic Sith" or "generic Jedi" or "Generic Bounty Hunter" categories all throughout SW lore. IMO, I like this. Its far less scripted, its not ground breaking and from an RP stand point it lets you differentiate a little bit from others. (maybe your father was a Sith but you became a trooper, have some sensitivity so can do say a force choke but never learnt beyond that)
And as far as the races go...there are examples of TONS of Jedi that have fallen and/or Sith that have come back to the light side of the force. Its not race exclusive by any stretch, perhaps less common but doesn't mean its not possible. Revan went light to dark back to light. Anakin when light to dark back to light at the very end...it happens. Every character's destiny is different, there is no set law saying they cant change their ways. I find the idea of an entire race of people destined to only be evil completely unrealistic. That would mean there is no way one could be say...raised on a different planet, have a different opinion then others etc. And when it comes down to Human(oids) the one thing we see most often, is we all have different preferences/ideals/moral compasses, why should a Sith Pureblood be any different?