It's possible that I misconstrued the meaning of your words; not being a native English speaker myself, this happens on occasion. I was going off of the word "vibrant", which I understand to mean among other things "vital" and "energetic". The opposite of that is to make something sickly and weak.

I think you may indeed be missing some connotations: in policy debate on immigration and multiculturalism, what one side might call "a vibrant and diverse neighborhood", the other might call "a slum filled with hostile foreigners with no inclination to integrate" (see this blog post, for example).

So someone who says that "you shouldn't make your country more vibrant and diverse" isn't expressing hostility to vitality and energy, he's objected to the loaded words and underlying assumptions.