Perhaps draw a clear distinction between Un-American and illegitimate Trumpublicans and the party known as Republican, a party that may, or may not restore itself to legitimacy.
For example:
Trumpublicans tried to destroy our government from within. They have corrupted values that Americans, whatever their party affiliation, have long taken pride in.
Today we begin to undo the damage they have done to our nation. No more will executive agencies do the bidding of a corrupt man. It is the will of the American people that must be done; our collective will, as expressed in the body of law we have evolved on the path to creating a more perfect union.
All vestiges of Trumpublicanism will be purged. The transformation begins right now, with a commitment to ensuring this government upholds the rule of law, serves the American people, ensures equality of opportunity, and protects our freedoms, our families, and our collective future as a nation.
Whether the Republican Party can recover legitimacy from the destruction of it's values by Trumpublicans remains to be seen. We hope they do and we hope they join us in our effort to serve you, the American people.
Seems this kind of distinction offers a way out. I don't know that branding all people who consider themselves to be Republicans as members of an illegitimate party would be effective. Making a distinction offers a "way out" of sorts -- a way for someone who still sees themselves as a "Republican" to distance themselves from the insanity of Trumpublicanism.
But neither can we treat the current regime as if it is a legitimate political party.
Just a thought.