The human mind is very good at seeing what it wants to see (especially when we are looking for something specific) and we often look for racism. This is a good thing! It helps us avoid in in situations where it could have been ignored. Unfortunately it can lead us to mistruths some of the time. Personally, I felt Q was vigilant, serious, and trustworthy. I never got a barbaric or unintelligent vibe from him but more of a stoic vibe, which I hadn't really second-guessed. In my mind, he was silent because he was more concerned with doing his job well and keeping a constant eye on the situation than learning/speaking the language. Not because he wasn't smart enough to, but because he had other priorities. Plus, having someone you trust around to sort of "translate" or fill in the blanks for you often leads to quieter people. Children with older siblings do this often, and won't learn to speak until later on.
*shrug*
It really is a matter of perspective from the reader though, and just because one person sees something one way doesn't mean everyone does, or that everyone has to.