[@Ultimate Spidey]
So SHIELD was a rumor for several decades before it became public knowledge during a massive crisis with superheroes (something like the battle of New York, I haven't decided yet). To the general public Hydra would mostly be known to WWII buffs, that is before they resurfaced in control of SHIELD. The reveal that SHIELD was being controlled by Hydra was global news as many superheroes, notably the Avengers, very publicly fought them, causing much damage to many cities and resulting in many deaths. So yes SHIELD and Hydra are common knowledge, and that's why many will be against the Avengers becoming a replacement for SHIELD.