That's still just a conjecture of a meaningful effect. Recruiters are able to change tactics in response you know. You're just naively assuming that those old tactics worked better just because reddit itself changed, but it could very well be the case that the more extreme rhetoric only attracted people who were already extremist and turned off moderates, but a more moderate approach that's now required could funnel more moderate people into an extremist pipeline.
"Off reddit" is just a win for reddit's PR, and that's why they did it, and no other reason and no other effects can be inferred.
The claim you are addressing is a separate one from the fatpeople hate story.
And that claim is evidenced, It’s not conjecture. I dont have it handy on me, but we have mapped out the ways people are recruited, and things like fatpeoplehate, coontown, are the funnels for groups to find new recruits.
There’s several others on things from ISIS to hacktivists. The mechanism is the same, heck - “red pill” is the term for this, it’s actually quite known.
"Off reddit" is just a win for reddit's PR, and that's why they did it, and no other reason and no other effects can be inferred.