I often do the same as these guys when I see riders going the wrong way because it CAN be the end of the world (your world, or theirs, anyway) if you are nearing an intersection and bikes (or even runners) coming at a good speed on a perpendicular speed make a right turn on you (and in a few other types of circumstances as well). The incoming riders/runners might not be in their right (should have come to a complete stop before turning right...) but it will be the end of someone's world anyway.

As for being loud, well I don't know of many ways to say something to another rider gently or subtly and getting the message across when I'm riding my bike (wind, speed, etc. make it difficult to send anything but bold messages).

Using and sharing the road is all about anticipating the other's conduct.