Good and evil don't exist, but if you say those words to someone untrained they automatically translate it to [things I like] and [things I don't like]. These things do indeed exist, so it intuitively sounds wrong to them.
Good and evil don't exist because there's no external way to validate or invalidate your preferences. As indeed should be the case. Stuff that exists exists. You like what you like. The rest of the world can say or do what anything at all and it doesn't change that you like the things you like.
It's merely that if you like getting high on heroin, but also like not dying of opioid overdose, then upholding the first preference over the second is imprudent. The conflict is internal. (Shocking news: consciousness is subjective, not objective.)
You know this next party already, but I'm going to say it anyway. The [morality is social control] crowd is far more correct than not. It's common to identify [stuff you like] with ingroup and [stuff you don't like] with outgroup. Naturally this is done by those who can control what counts as ingroup and outgroup, thus controlling your ""moral"" compass, thus controlling your actions. Harming the upper class, no matter how parasitic, is always defined as immoral. Self-sacrifice is a myth spread by the most selfish, who offer the clarion call to sacrifice your interests in favour of theirs.
P.S. Most humans have no personality. They have no internal texture aside from maybe [hunger is bad] & [sex is good]. Changing their fake and pretend preferences for other fake preferences is trivial and largely meaningless to the human in question. If saying up is down and black and white lets them secure their next meal, it's all the same to them.
P.P.S. They can't have good taste because they have no taste at all. It seems bad merely because entropy; there is far more bad art than good art.