That's why I think people, myself included, should probably cut the Jake Lloyd/Hayden Christensen/Sebastian Shaw portrayal of Vader outside the suit some slack.
You had a well meaning, smart kid that genuinely liked to help people, taken from his mom at a young age by the Jedi. He was sad about it, like any normal child (or human really) would. Instead of being comforted by the evil Jedi, he's constantly chastised for missing his mom and friends. The Jedi tell him it isn't natural to fear losing his loved ones. They tell him it's wrong to love. Obi-Wan hates him as soon as he's introduced to him ("Why do I sense that we've picked up another pathetic life form?" = equating this poor kid that just helped win them a new generator to continue their mission to Jar Jar ****ing Binks), Mace Windu and Yoda chide him from the very beginning.
Then the only Jedi that believes in him as well as his potential to do good, dies. He's then stuck with this weird cult of robed space weirdos who don't believe in him at all. Then on the crux of adulthood, all the poor guy wanted to do is bone his nabooian childhood crush like any normal hormonal teenager, but you got Obi-Wan, Yoda, Windu and the other Jedi bitching him out 24/7.
People call Christensen's performance wooden, but think about it, this is a man who was born into slavery, separated from his mother at 9 years old, had to hide his emotions, marry in secret and essentially shamed himself for having kids with his wife. His outbursts are those of frustration. Every rant against Obi-Wan, the sand people, and the Jedi are justified ones.
He wasn't just killing younglings in that scene, he was killing a part of himself. The child that couldn't save his mother or friends anymore. The child born into a life of pain and suffering.