“This is not who we are” is not a literal statement. I wouldnt make any sense taken as one, since its used in response to news of actual events rather than hypotheticals, and if taken literally, it would be very similar to “I am not doing what I am currently doing” which is paradoxical.

Rather, it is a statement to others of ones group that their behavior is problematic and therefore that they should stop it, using an emotional appeal that invokes values those problematic members of the group are expected to profess to have.