Is diversity in a country bad?

This is probably the most weird or even maybe most stupid question I've thought of in a while but I really need an explanation or to hear other people's views on this.

So this YouTube video popped up in my feed and yes not the best example to base on. And the guy was complaining about this tv show being used as propaganda to I think I'm not so sure, white German children or something? I don't really know what he was on about. And I even got more perplexed when I read the comments which honestly you'll just have to read them for yourself, now i can see why from an objective perspective anyone would complain at the clips of that show that I saw out of context, but the comments from the commentators on the video didn't really seem to be criticizing the show in the manner I was expecting if anything they all see very anti-immigration and some just flat out prejudiced and racists and I don't know man, it just got me thinking about this very question I present to you.

Now I've done a good amount of just shallow looking it up online if immigration really effects a country in a very negative way and I wasn't very satisfied with what I got e.g.

"Immigration significantly impacts a country by driving economic growth, filling labor shortages, and expanding the tax base. However, it also introduces challenges such as increased demand for public services, potential downward pressure on specific wages, and the need for successful cultural and social integration."

"Immigration is neither inherently good nor bad; rather, its overall impact depends entirely on a country's specific economic conditions, policies, and management strategies. It brings significant opportunities alongside real challenges, with different groups experiencing the effects in contrasting ways."

Now I know life isn't all that black and white, there isn't necessarily a yes or no to such a question in a simplistic way as they're is a lot of nuance and such, but the comments on that video really aren't that nuanced and since the election of Trump and just the general swinging to the right of world politics across the world, one of the major trends I see people bringing up over and over again is how immigration and immigrants are taking their jobs and are destroying the economy and I personally held the view for a long time that the answer is not that simple and that's just not the answer based on some studies and factual evidence that they really don't but with the uptick with such views across Europe (like in that videos comment section which again is not the best source to base world views of people but it's what got me thinking about this seriously) and in the US I really just wanted to ask the question?

And honestly what even is the end goal of being anti-immigration, now I've seen people argue that it's for self preservation sake and I can actually understand that, but way too many times too many almost without fail people who claim not to be racist usually infact are and just hate people who don't look like them. And again yes it's not that simple but I personally feel like from the people I've talked to who hold that view a good number are just racist and don't like thinking of including people who don't look like them in their tax money and would rather have them suffer and not be well off, which again comes back and usually bites people with this view stance cause if there's something history has taught us is that today they'll come for the other and you'll be fine and tomorrow they'll come for you and that's usually when I see people care, when it's affecting them.

And to raise another question is diversity even possible? because I heard a quote that went something like "if we woke up in the morning to find that all things that divide us are gone, by the afternoon man will have already found something to be prejudiced of others about"