Hey kiddo, have you ever heard someone say "it's wrong to do that because it's just not right"? That's called a moralistic fallacy, and it means that someone is using their personal beliefs about what is right and wrong to try to prove a point, without any real evidence to back it up.
It's like saying "that cake is bad because it's just too sweet!" Just because you don't like sweet things doesn't necessarily mean that the cake is bad. Similarly, just because someone thinks something is morally wrong doesn't mean it actually is.
In science and logic, we need to use facts and evidence to make our points - we can't just rely on our feelings or beliefs. That's why the moralistic fallacy is considered a mistake in reasoning. So remember, just because something seems wrong to you, doesn't mean it's actually wrong. We need to use reason and evidence to make the right decision.