They don't really believe Trump is an existential threat, they're just infinitely annoyed by his cultural presentation and lack of class

They're infuriated by the second hand embrassment they feel when they see him on the global stage and by how annoying he's made members of their own family

Alot of this is just inter-family suburban squabbles being directed outward

"Before Trump my aunt Martha was a decent respectable republican who believed 95% of everything I believed, then Trump came along and now she's an annoying dingbat who ruins all our brunches with her crass politics"