I don't think we'll ever know how Abrams hoped the story he started in TFA would be developed. Everyone is too professional to get that explicit (I think!). But I wouldn't be surprised if this was exactly his intention, and it was a fairly common way of seeing Kylo Ren (hence the popularity of the emo Kylo Ren Twitter). I definitely shared that interpretation, too.
I suppose we do know from Adam Driver's hints that some form of redemption was always expected for Ben, but I don't think Abrams had any plans of it being through Reylo. I think he expected it to be through Han and Leia (and maybe Luke), letting Kylo Ren know it was never too late to metaphorically come home.
In case it wasn't clear, I don't mean that Ren's victims are nobodies within the context of the fictional universe. I meant that they are literally not actual people, as in this is a fictional story. One of the things that's been interesting for me in all of the sequel trilogy discussions is seeing the very different ways we all respond to fiction. And there's no wrong or right with this--there's simply what's personally satisfying.
But I do think it's important to acknowledge that Kylo Ren fans are probably not actually arguing that murder is no big deal but rather that they're responding to the symbolic journey.
Even the Ben Solo-deserved-better people, IMHO, aren't handwaving away massacres... they're seeing Ben as a child who was abused and manipulated into doing horrible things that he didn't want to do and who never had a chance to live independently.
That's why I'm personally more bothered by the handwaving of Poe's mutiny than I am the Bendemption. I get how Kylo Ren's story can function on metaphorical level for people who have hurt friends/family members because of potentially forgivable things (e.g. addiction, unrealized neglect), so I can respond to it symbolically. But I don't get how Poe's story functioned that way, and so I can only respond to its literal level.