No, they are anti what they perceive immigration has become, a threat not just for resources, houses and whatnot, but an existential threat to the country they think they live in and consequently their own identity. There are racists that are exploiting this and fanning those fears, let's state that from the get go, but they've never had this level of traction before and that traction comes from a mass rejection of multiculturalism.
What these flags represent is a political statement that states in no uncertain terms that there's an indigenous population in this country, that there is an over arching culture and those that choose to live here must recognise that fact. That citizenship brings with it benefits yes, but it also brings obligations and those obligations should include a commitment to integrate into the prevailing culture and to learn English. Cultural identities are sacrosanct but only insofar as they comply with the laws of the land.
Cultural festivals, religious worship, have at it, great, we're a free country, but that country is Britain and it's more than just a land mass. No more "diversity is our strength", it's not, it's a lie and people know it. More unity is our strength and that must come with a new social contract between the people and the state based on honesty and the pursuit of common purpose. Less all cultures are equal, they're not and certainly not in a country with an over arching culture like ours, less DEI and more "When in Rome".
If "progressive" folk in here don't like it, fine, do nothing and see how that works out, as I stated earlier if reasonable people's reasonable demands are not addressed reasonably they end up being addressed unreasonably.