The assertion is that his friend's acquaintance with KKK members was effective at helping them leave. But we can't tell how effective unless we know how many people would have left without the friend's assistance.

Reread what they said; it's not their friend and he made no claims to efficacy. Your response seems off-context.

You're correct: it wasn't their friend, it was something they read.

It does sound like they're making a claim to efficacy. It says "one by one managed to turn them away". That's the part I'm asking for clarification on.

The anecdote about Daryl Davis is the preamble, the last sentence is their point.

I'm not saying that's not a valid point of conversation, I'm saying it comes across as off-context to the point where it seems a little like bait.