You must get at least some of your beliefs right, before the remaining ones can be wrong about anything.

Brute force attacks on passwords are mostly being wrong about things. If beliefs are singular things, like a single attack on a password, EY's claim isn't true. If beliefs are more than one thing, EY might be correct. If every single belief about being in a new social setting is distinct (not knowing cultural norms and knowing part of a language are two things), then EY's claim isn't true. If beliefs come in clusters (not knowing cultural norms but knowing part of a language are not things that can be separated). And if (as Popper suggested) scientific knowledge is based on falsification of bold conjectures, then scientific beliefs don't have to have a little right in them to be wrong later.

So all this suggests that you should be willing to accept that you might know a little about morality. Nothing unquestionable, perhaps, but an initial state with which to start questioning yourself. Baked into your brain but not explicitly known to you, perhaps; but still, that which your brain would recognize as right is what you are talking about. You will accept at least enough of the way you respond to moral arguments as a starting point, to identify "morality" as something to think about.

Correct, as long as some people are not considered human beings. Some people straight up don't have that baked in recognition of right and wrong. These include infants and people with mental problems.

It's not perfect information, surely, or absolutely reliable, but you have someplace to start.

The place we start is the place we start. The foundation is the starting pistol, not a blank slate or a baked brain. We hit the ground running and go from there.