Assigning every possibility the same amount of credibility isn't providing as much quality in your feedback as you could be. Realism and focus is a good thing. Having an "open mind" should not be equated with being willfully ignorant of the game's structure, its resources and various developer statements.
I think it's best that with any possible playable species to keep an open mind on how they could work and be implemented. Rather than just saying 'No', we should try to see as many possible ways they could be introduced as there's always some sort of surprise that could happen with the game.
I'm not saying (and neither was the person you were quoting) that we should just say, "No," and ignore the possibilities, but the problems need to be acknowledged, not dismissed. And a lot of these problems are more severe than you tend to treat them - for example, simply saying, "I don't mind," regarding alien voiceovers is not adequately addressing the severity of that particular barrier.