I really don't see extreme liberal values- currently- as a threat. At all. The GOP has a racist president who lies non-stop in charge of the country and they are stacking the courts. Far more likely that the extreme right is going to be the issue in the near-future.
Racism- Is on the rise. It was slowly dying, IMO, Trump and co. have revived it full force. Just remember, kids, there are fine people on both sides of a Nazi rally and their protesters.
Sexism- Also on the rise. "She was bleeding from her wherever" "Nasty woman" "Okay sweetheart" When the right is led by a person who is clearly a racist, sexist, narcissistic moron- and said moron was elected by 50 million people- you can't tell me we're getting past this.
LGBTQ- Fortunately getting better, no thanks to the GOP who is still trying to block marriage equality, equal adoption rights, (wtf man let the kid have a home over the foster system), and making sure that that person who looks like a man actually uses the ladies room since he was born a female.
The radical left has Antifa, which to my knowledge has not yet resulted in anyone's death, (they're still horrible, in my book, just pointing out the differences here). And Antifa is a problem and should be dealt with. But I don't feel like Antifa threatens the very nature of this country. They simply aren't big enough.