There were 1.2 million abortions in the USA last year. Hitler was one person. Would you kill 1.2 million to ensure that Hitler wasn't born?

Your argument is not logical and is morally repugnant. It's far worse than anything Mao Zedong dreamt up in the purges, and those were far worse than Hitler.

How many wonderful scientists, artists, poets, musicians, etc were not born?

The ugly aspect of those statistics is there a much higher percentage from certain ethnic groups. In a way it's a genocide of those ethnic groups.
[link to www.abort73.com]
A very high percentage of minority children are aborted.
"abortion kills minority children at more than 3 times the rate of non-Hispanic, white children. The rate is even worse for black children"

"...black women make up 12.3% of the female population in America2, but accounted for 36.4% of all U.S. abortions in 20063 – that according to the Centers for Disease Control (CDC). The Guttmacher Institute (AGI) puts the percentage of black abortions at 30% of the U.S. total"