I don't debate on Yahoo Answers anymore because, like others, I find "the stupid" there to be oppressive.
They seem to be following the typical line of debate. The claim that "many scientists" believe the Van Allen belts to be impassable to humans is just false. The claim that we haven't studied the Van Allen belts enough to know whether we can pass them safely is also just false -- with a caveat. You can always stand to know more about something, and we are constantly refining our models of the trapped radiation belts. That said, you have to remember that radiation affects more than just biology. It also affects electronics. And compared to vertebrates, electronics have poor self-healing properties. Quite a lot of private commercial spacefaring involves operating unmanned spacecraft in and through the Van Allen belts. There is considerable monetary incentive to know as much about the trapped radiation as possible, and considerable monetary incentive to getting the relevant engineering right, including proper design of electronics to withstand the radiation environment.
The claim that shielding was provided to facilitate transiting the Van Allen belts safely is half right. Which is to say, there was no component of the command module specifically designated as radiation shielding. However, the construction of the CM for its other purposes, chiefly aerodynamic re-entry, incidentally provided about 7 grams per square centimeter of effective shielding, which is enough to attenuate the effects of transiting trapped radiation along the Apollo trajectory. And it's the trajectory that is the real game-changer. The Sun-Earth-Moon system exists in a three-dimensional space governed by four geometric planes (or more properly, the normal vectors defined by them): the ecliptic, the Earth's magnetic field, the Earth's equator, and the plane of the Moon's orbit. The ecliptic governs the direction from which solar particles arrive. Earth's magnetic field dictates how they are trapped into belts. The interaction of those two dictates how the fields of trapped radiation are shaped by the interaction of magnetic entrainment and bow-wave effects. The Earth's equator affects the orbits around Earth that may be easily obtained from a given launch site, payload, and vehicle. Finally, the Moon's orbital plane interacts with Earth's equator to recommend trajectories for transfer orbits. All that combines to produce possible transfer orbits at inclinations that miss the most intense portions of the Van Allen belts. This is problematic because most diagrams of the translunar trajectory the public sees are simplified to suggest it all happens in a single plane. it does not.
The trapped radiation belts are easily avoided in the Apollo scenario by trajectory design. However, future missions may place additional limits on trajectory design that preclude the Apollo methods. It then falls to attenuate crew radiation exposure by other methods while transiting trapped radiation.
Other sources of radiation such as galactic cosmic radiation and solar events become more of a problem as mission durations increase. This is often what people refer to when they quote recent NASA authorities as saying they must revisit the radiation exposure problem. Laymen wrongly dismiss this as a suggestion that Apollo didn't solve them. Rather, Apollo solved them in a way that was allowed by the parameters of those missions. We now contemplate different parameters. GCR accumulation becomes a factor for longer missions the same way staying out in the hot sun for longer increases the chances of sunstroke or heat exhaustion. Organisms can withstand a two-week drizzle of background radiation with few if any ill effects. Less so for, say, a two-year mission.
Similarly solar radiation becomes a problem for longer missions. Avoiding solar events such as flares or coronal mass ejections was largely a statistical argument for Apollo. The odds of anything like that happening in a given two-week period, at lethal strength, in the direction of Earth-Moon were simply acceptable risks. The statistical argument doesn't work for longer missions in which the probability of a dangerous event during that period is greatly increased.
