I just made the same point as Ruby. <3 Sorry!
Look at the issue from another standpoint: The United Federation of Planets is the city on the hill. It's the galactic utopia. There is no poverty, there is no hunger (both untrue, but for the most part on the nice Federation worlds it's true), and their military is taught to seek peaceful solutions even after you've been fired on first. They're open minded and open handed. I can't imagine the Federation saying to even a Romulan, "Nono. We won't even give you the chance to come be part of Starfleet and the Federation."
Does that sound like the Federation or Star Trek to you?