In this case you were ok. You sound like a reasonable fellow. He was playing mr. local high and mighty. Territorial, like a local surfer
On factory waters like chehalis/vedder/capilano during the salmon runS IF there is a decent amount of space between myself and an upstream angler I will just drop in and give a head nod , a wave , some sort of acknowledgement to gauge the situation.
During Steelhead season on ANY water I will always always always ALWAYS start at the top of the run and rotate in. Everyone should do this. If the run is busy , or the head of the run is occupied, I will sit and wait my turn. If I drop in , even at the tail out with one other person at the top , I will ask and MAKE SURE the angler ahead of me is ok with this.
Early October I was up in Skeena country spey fishing in the kalum and copper systems. GOD *&%ING help you if you drop in on someone anywhere in a run up there without having a conversation and asking first ahaha. It's like the locals who fish the Thompson. Things can get heated very, very fast.