I try to block those spammers as soon as I detect them.

I think the point is that the convenience of being able to ride a bike without having a helmet at hand is something beneficial for the group. That it, there would be fewer cyclists if wearing a helmet was mandatory, and that would harm cyclists as a group.

By all means, if you consistently go over 20km/h on bike, wear a helmet, as at that speed it’s starting to get dangerous.