No because it's not on us to make moral distinctions between someone who is gay and doesn't want to make that information public, and someone who isn't gay and is being falsly blackmailed.
Publishing the DKIM keys makes both cases harder because you no longer have authenticity claims. Neither claim has authenticity value and instead is just a "their word versus yours" situation.
Humans are terrible moral adjudicators, and acting off of universals leads to repugnant ends. The truth can absolutely do terrible damage and still be the truth, but being the truth doesn't remove value from privacy. Put another way - would it be moral to publish your full medical records in the public? After all, they are the truth...
It is on us to make moral choices. You are suggesting we do so by making email repudiatable in order to protect a hypothetical person from being outed via stolen email verified with dkim.
So far as I can tell this has never happened in history and logically neither blackmail nor public harm via exposure of sexual orientation particularly requires dkim verification.
It looks like you are asking us to give up DKIM verification which could and has aided us to verify politicians leaked emails in search of a purely hypothetical gain that may never materialize by suggesting that we both must and must not make moral determinations.
When an angry mob goes after suspected homosexuals, do you think they stop to authenticate DKIM signatures of emails? I'll give you a hint: no. In fact, it's hard to imagine any scenario where anybody goes through the trouble of authenticating e-mails of a "normal person" who is persecuted of something other than crimes.
Shouldn't we privilege protecting people from lies vs protecting people from the truth?