It wasn't similar to a Holocaust, it was a Holocaust. I never think that Ethic Cleansing comes close enough. Any books painting a jolly life of a Nazi during the European Holocaust certainly wouldn't have made it to a TV series and that was in 1974
The TV series was inexplicably popular bland suburban pap, but it certainly wasn't alone in its 'othering' and whitewashing of Native American genocide -- look at pretty much every western ever made until slightly more self-aware ones like Dances With Wolves and others subsequent to it started being made, where 'Red Indians' are either actively evil savages or expendable gun fodder. And I think DWW was around 1990 . Not many TV writers were interrogating the myth of the pioneer West in the 70s.
I think the novels, while obviously hugely problematic in the way they portray Native Americans being shoved off their land as the 'natural' consequences of white settlement and of course Ma and others' fear and hatred of 'Indians' are at least slightly more nuanced in some ways, certainly for a children's book written someone who was pretty reactionary AND using the limited generic vocabulary of the pioneer childhood book, which was never going to be about NA abuses.
Countering Ma's anti-'Indian' prejudice is the more sympathetic Pa's respect for individuals, like the NA chief who prevents the slaughter of the white settlers (whom Pa stands and salutes, and who is actually named, rather than being Random Indian) or the elderly man who comes to warn the town of De Smet about the long winter, to whom Pa listens, when the other men are jeering. (Though yes, weather-warning man is depicted in deeply stereotypical ways.)
And even when I was quite small and reading LIW for the first time, I found the end of LHotP, when huge numbers of NAs all leave camp and ride West on the path outside the Ingalls' house, mysterious and fascinating. It's depicted as grandiose and deeply sad, though Laura doesn't understand why (and also wants a cute 'red' baby), and the end of something, and Pa's explanation, that 'that's what Indians do, they go west', is clearly inadequate. And of course the Ingalls themselves leave shortly after, as troops are supposed to be coming to evict them.
That's another thing LIW whitewashes in the novels -- in the fiction, Pa thought the land they settled on was going to be 'opened up for settlement' (obviously, as though no one already lived there 
), and it's presented as a mistake. But in RL Pa, who was a far more rackey and dishonest character than the Pa of the novels, deliberately squatted on Native American land, knowing it was illegal.
Everything in the novels is tidied up to suit the pioneering myth, and of course the novels are powerfully self-censoring about the life Laura was actually drawing on -- not just the death of her baby brother and how little privacy for sex and birth there would have been in isolated situations, but the fact that Pa often cut and run from debts in the middle of the night, and that Ma and the girls actually worked in a rough railway hotel.