Getting off the Nazi side is step 0. It’s the bare fucking minimum to even begin the process. They aren’t magically forgiven just because they were affected by their own shitty actions.
I agree that the left is particularly bad about bashing on people who are thinking about switching sides. People often say that the right is a cult, but that’s because it has a LOT of the indicators of being an actual cult, including using cult conditioning on its members.
A large part of cult conditioning is warning your members that safety can only be found within the cult. Telling cult members that the outside world is hostile and out to get them. And then they intentionally send those cult members out into the world, with the mission of being annoyingly aggressive proselytizers. And when they’re naturally met with hostility during that mission, (because of course they are, nobody likes the random door-knockers and street-corner-shouters trying to convert them), it confirms what the cult members have been warned about, and drives them deeper into the arms of the cult.
And attacking someone who is thinking about leaving conservatism plays directly into that same cult conditioning pattern. The right has spent a lot of time indoctrinating their members to believe that the outside world will be hostile. And attacking a former conservative only confirms what the right has warned them about, and pushes them back towards conservatism.
But that doesn’t mean we should welcome Nazis into the group just because they were attacked by other Nazis. They’re basically saying “okay, maybe Nazis aren’t all good.” But then you dig deeper, and they’re often arriving at that statement by saying “yeah the Nazi-on-Nazi crime is an issue we need to address, to keep the Nazi party strong.” They’re viewing the entire situation through a fundamentally skewed lens. And someone saying “maybe Nazis aren’t all good” is worth investigating, rather than taking the statement at face value and welcoming them with open arms.