there are plenty of left-leaning memos and examples that show similar tone towards right-leaning and/or conservative or libertarian thinking. That doesn't imply not being open to discussion so much as showing one's bias. There's definitely a matter of levels to one's opinion, experience and yes, some level of conflict.

When going into a situation where you've been at the back hand of such bias, specifically in a workplace, it's often hard not to show at least some condescension. Look at any number of public feminist actions and statements, for example.

Yes, both sides do it. That does not justify or excuse it, especially if your goal is to encourage discussion.