I do the vast majority of my riding on the south shore of Long Island and only occasionally encounter that kind of horn blowing and unsafe passing.

That said, the van driver did not brush past these riders, he/she did give decent clearance (from what. I observed) they were just pissed off that the bents were so far into the lane.

One has to wonder though that on MV, it doesn't take forever to get places, unless it's Friday and the ferry just got in. It's just not that big an island.

I thus assume that motorists are tired about having to share roads with poor shoulders and with a lot of cyclists using those roads.

The bent riders were in a no win situation. The shoulder occasionally disappears, then it's better, then not, but better to be taking the lane then riding the white line and getting passed too closely, which is the only option. I will typically just slow down at times when I get a decent shoulder and let a whole lot of cars get passed me, the move back into the lane, trying to give the motorists a break when I can. Just like any slow moving vehicle is supposed to do.