There is another issue with FAE, but I am not very good at expressing it clearly. Basically it seems there is a very strong assumption in most minds that behavior that is as a value judgement can be judged as bad must be unusual - that what most people do is "per definition" not bad, just "normal". In other words, we tend to abnormalize wrongdoing. Terms like "he is a sick fuck" suggest that wrongdoing comes from abnormity / unusualness.

Now if FAE says people are not actually that different, it suggests either that we should not blame wrongdoers or we should blame everybody.

To me the second makes more sense. If a behavior is unacceptable, even if it turns out that everybody would do it if the circumstances would be "right", it is still unacceptable.

Thus, we end up with having to say that we need a secular, atheist version of "we all are sinners".

Seriously, what else is there? Either you accept the unacceptable... of pretend wrongdoers are special, different, "sick"... or you say most of us are in a way, "fallen".