As a bicyclist, I'm constantly told how dangerous bicycles are. Usually, I get a blank look when I explain, bicycles are very safe, it is the cars that are the dangerous part of the equation. Now I'll have to add fast billing ambulances to the list of dangers.
Cars are more dangerous than bicycles because they’re larger and faster, yes. But when you compare cars vs. bicycles on the same road, together, bicyclists are in more danger. I can only surmise the people that tell you “bicycles are dangerous,” are just looking out for your well being and meant “you’re putting yourself in danger.”
Unfortunately, roads were designed for cars first. Even more unfortunate, people are not accustomed to sharing the road with bicyclists and only glance at their mirrors to check for large familiar cars. Thus, to say that “cars are the ones that are dangerous,” implies you think bicyclists have the de facto right of way and everyone should adjust to your presence.