Here is a template for you to copy and paste, then alter before sending to your MP.
Make sure you change the words even if it's only slightly to reduce the risk of it being blocked.
I am one of your constituents. I am writing to you about to the racially motivated police brutality, that happens here and in America, and the violent reactions the protesters campaigning against it are receiving.
Donald Trump actively encouraged the military and the police to use force against the protesters. He has also publicly classed anti-fascists as a terrorist threat. This threatens democracy and it has to be taken very seriously. To protest is a human right.
White supremacy is a growing global threat which must be taken seriously. The loss of real democracy is also a global threat and you must fight to protect it, with us.
It is essential that our government makes it known that it is not acceptable in any way. You, your fellow MP's and Boris Johnson must make it clear that we, as a country support the Black Lives Matter movement. There needs to be a public statement made. You work for the citizens of the United Kingdom, and you speak on our behalf. This is not a suggestion, it is a demand. Please use your voice to make us all heard.