The only protest that intentionally blocked emergency services I can think of was the antivaxxer "freedom convoy" protests.

But when you ask a random lib to think of a protest blocking emergency services they'll blurt out something about climate/workers/BLM/Palestine/etc. Talk about the freedom convoy and they'll get holier than thou about how unfairly those widdle science denwying fwascists got treated by the police when any Leftist protest ever was treated 100x worse.