Mandatory helmet laws make the number of injuries associated with biking go down. That is their purpose, and they are effective. Yes, some of that is people who would rather not bike at all than bike safely, and there are some non-linear effects from that, but it's still a net reduction in injuries.
There is a real need for society to discuss whether the value of reduced injuries outweighs the cost in terms of less cycling - for example more car emmisions, more traffic congestion, less easy cardio, etc. But to say people are less safe is just not true for the common definition of safe.
There is a real need for society to discuss whether the value of reduced injuries outweighs the cost in terms of less cycling - for example more car emmisions, more traffic congestion, less easy cardio, etc. But to say people are less safe is just not true for the common definition of safe.