If you believe helmets SHOULD be worn, you'll get people who tell you the scientific studies in favor of helmet use are politically skewed and part of a massive helmet industry conspiracy to make us all buy them, and that helmets don't really protect you, and that helmet laws only serve to dissuade potential cyclists from riding.
If you believe in NOT wearing a helmet, people will scream at you for setting a poor example for the kids, and tell you how irresponsible and selfish you are, and they'll tell you all about the time they fell over in the driveway and lived to tell the story because they were wearing a helmet.
It also seems the media world loves to propagate the fight by always letting you know the cyclist wasn't wearing a helmet when they were killed by a motorist ... as though they might have lived through being hit by that pickup truck whose driver was both drunk and texting at 50mph, if only they'd been more responsible and worn their helmet. The media would have you believe the vehicle driver was the real victim, and that the cyclist's demise was obviously their own fault, not that of the driver who "never saw them". The media will imply that the helmet would have not only protected their entire body from the high-speed collision with a multi-ton vehicle, but it would likely have made them completely visible to the driver, therefore helping to avoid the accident altogether.
Personally, I'm not sure where the line should be drawn. I can relate to arguments on both sides. I've actually fallen in the driveway while attempting to unclip from my pedal (back when I used clipless pedals) and felt my helmeted head smack the pavement. I've often wondered whether or not I would have experienced some kind of injury if it was my bare noggin, rather than a helmet-covered one ... but then I realize the helmet adds some size to my head, and it very well may have been just the helmet to hit the pavement, and a bare head might have never touched it. At the same time, I've tripped over things many times in my life while simply walking from one place to another, and have suffered no real head trauma. That being said, I've never crashed at high speed, and have no experience with what happens there. Also ... if I understand it correctly, the official testing for bicycle helmet certification is basically only good for low-speed incidents that involve something hitting your head from the top ... which seems a rather unlikely scenario. And even if it does offer some protection for a portion of your head, it certainly won't protect the rest of your body from a high-speed auto collision. The odds of surviving that are low, helmet or not.
So .... my official position is that it should be optional, but perhaps recommended, depending on the environment and type of riding taking place. I don't think they should be required, because there are many circumstances where they just don't make any sense for casual riding ... but I do think they serve an important function, and should be used when there's a potential risk. How's that for taking a firm stance?
Nevertheless, I do choose to wear a helmet when riding. Even if I'm not entirely convinced it will save my life, it does give me a little added mental security, as well as giving my quite significant other a sense that I'm being safe. But most importantly, it gives me something I can only get from wearing a helmet. You know what I'm talking about ... it's that special thing that tells everyone "Why, yes, I did just finish an epic bout of cycling."
Post-Ride Helmet Hair ... the BEST reason to wear a helmet!