First of all, there are many illegal depictions of Jesus and Christian imagery all throughout this country's "public squares." Public schools and government buildings regularly display Christian artworks and signage. And yes, they depict Jesus as white. Here's an example of one: https://www.aclu.org/blog/religious-liberty/religion-and-public-schools/if-you-want-fit-public-school-just-become
2nd, white supremacy is insidious and it invades everything. You are naive to think that it hasn't influenced the art world just because there are some depictions of Jesus as Black or brown. You even say yourself that you and other Christians are aware that Jesus was brown. So why the white Jesus paintings anyway? White supremacy. White people cannot fathom that their God might be anyone other than a white man so they rewrote history to depict him as white. That is literally white supremacy.
3rd, Shaun King is an activist to no one but white liberals. He is a fraud, a liar, a thief, and has targeted Black people, and Black women in particular, endlessly. He has been denounced over and over in the Black community.
A few sources: https://medium.com/@deray/on-shaun-king-351bd812318c
The fact that you think he is a representative of the current movement against police brutality and for Black lives makes it painfully clear that your involvement in BLM is surface level at best. Regardless of how awful Shaun is though, you, as a white person, don't get to tell Black people what is or isn't racist.
This entire writing screams of your discomfort as a white woman in confronting your own racism. Instead of addressing the white supremacist nature of society that literally reaches into every aspect of life, you decided to attack a Black man for taking this BLM thing "too far." The fact that only white people have clapped and commented on this article should give you some indication that maybe you're in the wrong here. Do better.