This reminds me of when my ex and I went through the adoption process to travel to China in 2002. Prior to being approved, a couple has to undergo serious sessions with a social worker to determine if they're able and capable of adopting from another country.
Our social worker posed this question: imagine you're pushing a stroller, and a friend/family member/neighbor says "good to see someone's trash is another persons treasure."
What the social worker was looking for, was how we'd handle the situation. Would we go off in a rage, lash out, name call?
Instead, we answered that if this came up: I/we thought we knew you. I'm very disappointed by what you just said. It offends our family.
I guess my point is, how do we handle being misgendered. In 10 years living full time, I've been misgendered maybe 3 or 4 times. One of best friends said he/him...to which I promptly replied "she/her." That's all I said, my friend realized her mistake and apologized. No harm done.