You don't mention where you live, but if you live in the U.S., every state has enacted laws stating that bicycles are vehicles that belong on the road. You own a car, not the road. The phrase, "share the road" means sharing use of the road not that a bicyclist must yield his or her use of the lane just because a car wants to get by.
Before we get to that though, did you know that the first paved roads in the U.S. were made FOR bicycles? That is right. Bicycles were riding on the roads even before cars.
Getting back to the law, the law states that bicycles are vehicles and shall ride on the road. Many of those laws state that bicycles will ride near the shoulder of the road EXCEPT where the BICYCLIST feels it is unsafe for an automobile to pass the bicyclist in the same lane. Essentially, for an automobile to pass a cyclist in the same lane safely, the lane would have to be a minimum of 14 ft. (4.3 meters) wide. In those instances, the bicyclist has the right to the entire lane. Regardless, a vehicle passing a bicyclist must give the bicyclist a minimum of THREE FEET. That is the law, if you don't like it, tough.
Also, the laws in many states allow cyclists to ride DOUBLE-FILE, contrary to what another poster has stated. The exception to this is when the group of cyclists are impeding traffic. The law does not define the term impeding traffic. However, at least one court has defined impeding traffic as going slower than the reasonable speed that the CYCLIST can maintain. So, the impeding rule, at least in that jurisdiction, is NOT defined by the speed limit but rather by a reasonable speed of the cyclists.
As far as defending "atrocious cycling actions", I am not doing any such thing. Cyclists are required to follow the rules of the road, just like any motorist. If a cyclist runs a stop light or stop sign and gets hit by a motorist that was following the rules, then obviously the cyclist was in the wrong. However, for every one of those instances where the cyclist was wrong, I could probably point out a dozen or more instances where the motorist was the one either breaking the law or made a manuever that could have potentially caused an accident and injured or killed the cyclist.
BTW, for any that think cyclists "use the roads for free", probably 99% of the cyclists in the U.S. also own cars and pay car registration and pay taxes which pay for the roads. Anyway, a 20 lb. (and sometimes less) bicycle carrying a 150 lb. rider does far less damage to a road way than any 4,000 lb. vehicle does.
As a cyclist myself, I can tell you that I can maintain about 17 to 20 mph (about 30kph) when riding. Which means that I can cover a mile (1.5 kilometers) in about 3 minutes. If the speed limit on the road is 30 mph (48 kph), a car can cover the same distance in about 2 minutes. If a car is behind me for an entire mile (1.5 kilometers) which is rare, then that car is delayed by only 1 minute. Is it really worth the possibility of killing a cyclist that a driver cannot afford to spend an extra 1 minute on the road?