"Western Civilization" is just some nonsense that racists made up. It's not a real thing. By "Western Civilization" fascists imply that they are unique and special snowflakes and all the good things in the world come from white men dominating, controlling, and exploiting everyone else. It's nonsense. It's bullshit. It's a false narrative. We're not trying to destroy "Western Civilization" because that's not a real thing that exists. By even acknowledging it and treating the charge seriously you're ceding the field to the Fascists and trying to engage them on their own bogus terms.

What do Plato's Republic and David have to do with each other? They're a thousand years apart, the product of people who spoke different languages, practiced different religions, and had wildly different norms and morals. Plus Plato was a bastard who advocated for slavery and all kinds of other terrible things. His Republic is interesting mostly as a historical curiosity in the history of theories of government.

Western Medicine? Pretty much exists entirely because of Arab Muslims who preserved and translated classical texts, which were then carried to Italy by Jews fleeing the Spanish Reconquista. Same with a lot of Latin and Greek writings. Same with science, optics, all rely heavily on Arab Muslims and not a few Jews. The famous Avicenna, whose works on medicine were so foundational to "Western" medical practices, is actually ibn Sina, a Persia/Iranian. Is Iran to be considered part of "Western Civilization"?

America's alleged Democracy is at best partially based on European theories of government - It draws strongly from the Haudenosaunee Great Law of Peace, which no one would seriously call "Western Civilization".

Christianity is key to "Western Civilization?" Which Christiantity? Europe alone has several of them - The Catholics, the various Protestant sects. America has added many more, including the flagrantly heretical Evangelicals whose beliefs are an almost complete refutation of conventional Christian doctrine, and the Mormons who are only Christians in a vague technical sense.

I could go on and on. It's all bullshit. They made up a rhetorical device, an imaginary Golden Age that they can claim to be defending or trying to restore, but it's just fascist claptrap. It was never real.