There can be a lack of crossover within the different disciplines of cycling, unfortunately some individuals in one discipline may have little understanding of etiquettes prevailing in the other. As a result, misunderstandings can arise between solo cyclists and those more used to cycling in groups, but I don't think any of the responses were unduly harsh.
Perhaps you should be trying to read the road a little further ahead, spotting potholes,litter etc. This would give you time to look behind and signal before altering course gently, avoiding a last minute swerve, in order to avoid the hazard.
As a solo cyclist I would want to survey the road ahead of the cyclist I was intending to overtake, perhaps drifting out to do this, then overtake without any vocal warning, but allowing plenty of space.