Interesting. The biggest argument to sway me that I hear against protected cells, is that they can be damaged, causing a short. (Shorts, heat, and charge state = bad) This can happen on a poorly designed light when inserting cell (who range in sizes), or dropping light.
My feeling is yes, initially, matching a brand of cell with light may be dangerous. But once you know what brand of cell works in your light, this danger goes away.... Then, the risk of light shorting (especially with corded headlamps) while near body is VERY LARGE, much larger than a light dropping, like, 20 feet and damaging a cell.
My bias is that, probably, high current lights are mostly toys and not tools. And if your protection is prohibiting the high current, this is for a safety reason--maybe a multicell light is safer for you, then.... My other feeling is from a good vendor, the protected cells are still cheaper than good 4 AA rechargeables....
So, I am mostly in the camp that when you get a protected cell, be careful when first inserting it into any light. Hope it doesn't get damaged by a poorly designed 18650 holder. (My fenix tk35 has springs on both sides, which is best design, I suspect. While some holders from dx, can be a bit hard on cell insulation on insertion.)
I still feel largely un-swayed by unprotected arguments. And think these people are typical over confident people who don't understand anything under triple redundant protection is no protection at all. Triple redundancy is NASA policy, for example. Not sure how this life rule exactly applies here, but double is better than single protection. Human reliance is folly. The only thing that is certain with people, is that a mistake is inevitable. People that don't grasp this have deeper flaws mentally that blind themselves to their own limitations. Most of us grow out of this 12 year old mind-set, but not all, I guess.