I know the way Democrats tend to think is that if they call for someone to resign/be fired, and the person doesn't, then the failure makes them look bad for reasons that can't be explained.
Obviously he should resign (fired, whatever) - he's shit and dangerous even by the current standards - but calling for him to resign isn't just about winning that battle. It's about showing you believe what you're saying - not just that it's "concerning" in the Susan Collins sense - and it's about keeping the story alive.
Normal people mostly don't hear about anything that's a one day story. If you don't give journalists something new every day they'll lose interest, in part because there are lots of things going on!
No one thinks Trump gives a shit what Jeffries thinks, but reporters need a hook!