But that isn't one off Google's workplace rules, and evaluation of whether or not someone is being "just" should be partially based on how well they apply their own rules.
If I say "this thing is permitted" and then punish someone for doing that thing, it should be unjust in your eyes whether or not you would have said "this thing is permitted."
No. Why do you presume they don't apply their rules correctly? And what makes you think this isn't one of Google's rules? A diversity class usually means diversity in the sense of protected classes, not political opinions.
"According to what you said in this post, It was completely just as Damore basically wrote a dissertation about things that were completely unrelated to any work done for any Google product."
My comment was explaining why i disagree with the above. It has nothing to do with whether I agree or disagree with Google's policies, past or present.
If I say "this thing is permitted" and then punish someone for doing that thing, it should be unjust in your eyes whether or not you would have said "this thing is permitted."