Is there a criteria for closing threads?

This is the most recent thread that was closed.

The thread had recently gained 2 new participants that proceeded to yell at each other. Having participants yelling at each other is not unique to this thread.

Perhaps the mods thought the thread had turned into a dumpster fire. This seems very subjective.

Now in this thread:Academically/Intellectually Gifted Education is problematic but necessary

I am being told to stop trying to derail the thread with discussions of race. I found this confusing because race is brought up in the OP and in a dozen posts by others throughout the thread.

It seems like the OP is allowed to say that tests are racist and I am not allowed to rebutt that conclusion because that would be injecting race into the debate and turning the thread into a dumpster fire?

Given these things, how is this much different from telling me that only one side is allowed to present arguments connected to race and education?