There are many, many people who use Trichlor pucks/tabs either in a floating feeder or an inline chlorinator and in any given year most such pools do not get algae for a variety of reasons (weekly shocking, short swim seasons, summer rains and backwashing water dilution, CYA gone over the winter, use of algaecides or phosphate removers, nutrient-poor water, etc.). So arguing against personal experience is going to be an uphill battle. It would be better to instead say that while such pucks are convenient, they have side effects that can cause problems for pools, including getting algae growth, and that there are alternatives that still use chlorine but without the side effects. Then refer and link to the TFP website and note that it has nearly 40,000 members and over a quarter of a million unique visitors per month during peak swim season. Leave it at that.