Technically both those cases are within the rules. You were the stand-on boat but choose not to be by reacting first. According to the rules you first course of action should have been five short blasts and only after they still did nothing should you alter course. Not saying that you are wrong but if there was a collision and you altered course first then you are not necessarily in the right anymore.
"So there i was, enjoying a nice leisurely sail on my hinckley, telltales flying clean, nice heel, good turn of speed, so smooth and calm my wife could read the newspaper on the bow. i see this other boat on an intersecting course, and figure if he needs me to give way, he'll blast his horn, or hail on 16.
I see him, he sees me.
Silence from the other boat, as we get closer... and closer.
Just as I am about to give way, he bears off, which was generous of him.
He gives me a dirty look as we cross. I notice his horn is nowhere to be seen...."
before you point out how wrong others are, make damn sure you are dead nuts right.