"How could it not?" isn't scientific, it's prejudice - you're assuming the conclusion. But there are so many example of it not happening. Here's another - Jews have been persecuted for centuries, kicked out of country after country, had whole families killed in the holocaust, and yet they repeatedly bounce back. Jews in Europe today are not a disadvantaged class despite their severe persecution from all sides before and during WWII.

If the effect is certain, how long does it take to wear off?