Did they abuse him?

[SourRoses]

Thank you @casportpony
That's what they did for sure, to both wings.

 

[Idaho Chicken Bungalow]

x2. That's probably what happened, but pictures help.
I'd personally consider the relationship ruined already after the confrontation.
Op, it's not great that your neighbors set their chickens on the property line and it doesn't sound like they're very experienced but you likely (inadvertently) caused the the pinioning or full trimming. They're probably trying to avoid ever having you coming down on them about chickens again after your last encounter, I certainly would be.

Can't they still fly if both wings were clipped (properly of course?)

 

[nuthatched]

Can't they still fly if both wings were clipped (properly of course?)

Not very high, if at all.