While this is true, that means that you can't discriminate against someone for how they believe. If they act in an unacceptable manner - for whatever value of unacceptable is used for am environment- then putting a stop to that is not discrimination.
So now you've lied to the speaker. Or you have to write that discrimination policy yourself, pushing it through HR and C-level.
And as the author says, that's what they would prefer, if they had all the time and energy in the world - and the sentence "We don't do that here" serves to say "Please don't make me have to write down a rule that says we don't do that here.".
It's like seeing a sign "Please don't pee in the washbasins in the 3rd floor mens' room". There's a reason someone had to put down that rule in writing.
What do the quotes signify here?