I've had coworkers with whom I have had cordial disagreements regarding politics and this isnt the issue.

When the head of your division uses the time before meetings to talk politics, it is toxic- the power dynamic isn't even. Coworkers can do the same when they publicly hold discussions and expect everyone to agree- the dynamic is off, and toxic. You simply can't have a civil, earnest conversation in a group chat or email setting, because it is too easy for the group to run away with a misunderstanding.