Going further into history like 1939 and killing hitler means no WW2 would happen, military wouldnt develop and USA/USSR wont engage in cold war.
That would be the biggest gamble in your life:
[A] he is replaced by a even worse fanatical anti-jew
[B] he is replaced by a better strategist that effectively holds the russians horders.
[C] he is replaced by a more reasonable person that eventually allows germany to mass produce modern wepons.
Regardeless of ABC, the murder of hittler could also trigger a ww2 or a civil war in germany.
If a civil war happens, you can be for sure that the west will back one side, and communism will back another, leading to a early cold-war that has more odds of ending in moscow being nuked to stop this "alternate ww2".
So yeah, is better to have the devil that you know, than a devil unknow.