A lot times this is a demonstration of the Boomerang Effect:

https://en.wikipedia.org/wiki/Boomerang_effect_(psychology)

Probably the cognitive dissonance subset of it.

I don't think it's an exaggeration to say a lot of zionists are brainwashed, or at the very least heavily indoctrinated and it takes actual deprogramming to get them to see objective reality. There are lots of interviews with people that were zionists and their experiences are amazingly similar to people who left cults.

The person you argued with sounds more like a casually propagandised media victim so the more evidence they hear, the more chance they have of coming around although "on the street" is usually not a conducive environment for that as it tends to be more confrontational.