Yeah, but I don't think most ordinary people are just looking for excuses to murder people. Somewhere along the way, these "ordinary people" were convinced that innocent men, women, and children were enough of a threat to slaughter them. By the end of the war when they realized that they'd lost, they might look to absolve themselves, but that doesn't explain the mechanism causing that behavior in the beginning.
I'd really suggest you read the book I mentioned, even just the preview pages available via Amazon. Your intuition doesn't match what is depicted. Their actions were not a reaction to the threat posed by the Jews, nor did they justify their actions in that way.
If you think that’s the only opportunity involved, then OK sure, but authority hierarchies offer much more. A feeling of control is what most people are after, and many other things they don’t want to readily admit. But whatever they want, I agree it’s unlikely to be ‘harming others’ but most people get what they do want from life by flattering authority. Different people want different things but most people get those things the same way, which is what matters here.