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.

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 was more objecting to your use of the word "diverse". And frankly these days "vibrant" has almost no meaning beyond being an applause light.

I don't understand your comment. Do you think statements like "the most efficient way to destroy our country is to do X" don't qualify as truths because they are "discovered under false assumptions"? It seems to me that such statements can be true and very useful to know even if you don't want to destroy the country, hence my original proposal. Maybe you're using a nonstandard meaning of "truth" and "assumption"?