If yes, is it also abhorrent when a group of workers at a company band together to influence the working conditions they all work under?
Nothing wrong with it! If some people in a neighbourhood want to buy up a parcel of land to prevent housing from being built there, there's nothing wrong with that. The issue sorta crops up when you start dictating what (structurally-sound) buildings others get to build on their own land.
If you want to reject private property altogether and go to some centrally-planned economic system then you've got a lot of work to do because even the fucking USSR was better at building housing than US cities are today.
When segregated neighborhoods collectively influenced which races could buy houses, was that abhorrent? I think we would all agree. When neighborhoods for neighborhoods watch groups, or clean up a playground, or build community by throwing block parties, they are doing great, not abhorrent things.
Conspiring to keep others out is usually abhorrent though.
Workers want good working conditions, home owners good living conditions.