You make some important points, but I do not think cock rings are hazardous. I've worn mine 24/7 for more than ten years now without any ill effects. I get hard, I get soft, I can urinate and I can ejaculate.

When I say 24/7, I mean just that. I rarely take mine off. I wear it under my street clothes, under swim wear, at nude beaches, under gym shorts, in changing rooms and showers at gyms and swimming pools, even to medical appointments. When I've dropped my pants in medical examining rooms no doctor has so much as batted an eye, nor has any doctor ever advised me that it was in any way unhealthy.