I was the one who flagged this users profile. I have no interest in discussing this with the user in question, but want to explain my reasoning to others who are reading this.
Why "Goyim Lives Matter" is antisemitic
When you google the phrase in question, this is the first result:
And yes, that's a modified swastika, and no, that's obviously not a coincidence.
Just as "white lives matter" is not a simple statement about the value of white lives, but a nazi slogan, so is "Goyim Lives Matter" not a simple statement about the value of non-Jewish lives.
The implication here is that someone - the Jews in this case - believes that non-Jewish lives don't matter. Otherwise, the slogan would not make sense. The idea that Jews are out to get non-Jews is classic antisemitism.
Antisemitic history of the user in question
The user in question has a long history of antisemitic outbursts and personal attacks. It should be obvious that someone with an antisemitic world view is not using the slogan "Goyim Lives Matter" - or "OpenBordersForIsrael" for that matter - neutrally. It is obviously a violation of the "no bigotry" part of the Be nice policy.
Personally, I also flagged the users profile because of their profile image - a hate symbol in some contexts - as well as "OpenBordersForIsrael" which used by people who are not antisemites might be acceptable, but where the implication is clear if used by people who have a history of antisemitism.
This user is an obvious troll, and is currently testing out the borders of what is acceptable behavior here - likely encouraged by unreasonably weak reactions in the past.
I appreciate the moderator intervention in this case and hope that moderators will stand by their decision to remove an antisemitic slogan. I also hope that they will keep a close eye on this user and take appropriate measures once the user does cross the border into unacceptable territory.