As a fairly new rider (about 2k miles under my belt) I'm going to chime in here as well. I personally will not ride without a full face helmet on. I like my life more than I like not being sweaty. I can speak of being sweaty with great experience after sitting in stop-and-go traffic on 95 many a times on rather hot, humid days on my black motorcycle with my black jacket and black helmet on. Now, that being said, there's nothing stopping me from opening my visor, and I've found that lets in some wind which is a huge relief. The thought of taking my helmet off never went through my mind, but I have a full-face with quite a few vents on it.
I don't think that those who choose to ride without helmets, or even those who ride in shorts and tee-shirts, are stupid. It's their choice to make, and it doesn't affect me, so I don't get upset about it. What I despise is seeing people ride without regard to others. Those who weave in and out of traffic, split lanes, pull wheelies, and just race down the roads are the stupid ones, IMO. I've ridden in states that don't require helmets, and my helmet stays on the whole time. To me, it's just not worth the risk, but to others it may be.
The reason I don't have a problem with the law requiring that all wear helmets is the number of people that are affected by the aftermath of an accident. Police, EMS, hospital staff, families, and even the people driving by are hugely impacted. I for one don't want my kids to see someone's brains spread across 50 feet of the road. I also think a rider without a helmet IS a hazard to others. I've heard rocks bounce off my helmet a few times, and they did nothing more than surprise me. Now, had that rock hit me in the eyes, shattering my sunglasses, what could have been no more than a simple "thunk" is now an impaired rider, with a much greater possibility of going down. Now, if this happens in moderate traffic, cars are going to swerve as the rider goes down, and could cause secondary accidents, affecting even more lives. Just my opinion, take it for what it's worth.