It is true that the algorithm does work against them, but it isn't a perfect bubble. I'm sure every racist on youtube had that same casting an obsidian sword video recommended to them I've been seeing. I spent a couple months looking into the alt right a couple years ago and I saw it for myself. The algorithm is just going by what gets the clicks so when a major topic comes along it's not too uncommon to see different sides pop up as long as they are on the same subject.

The backfire effect is real, but it's obviously not impossible for a person to change their views on something. Even something somewhat fundamental. It can take a long time for a person to come around and they need to come to terms with the truth on their own but it can be overcome. Even the things they don't accept today will be in the back of their mind when they come across something similar in the future. It's not easy to make that kind of change, but people do it all the time.