In my opinion/experience, a lot of the "slower charging is better" attitudes come from 2 different pre-biases from both ends of the environmental/political spectrum.
- 'treehugger environmentalists' who loved to smugly block the fast lane driving 50 mph in their Prius or 30-year old econobox on their crusade to save gas had adopted a 'slow-life' self-image. They still hate the fact that Teslas can be both powerful AND fuel efficient. Their only way to save face is to assume that faster charging must be worse and slower must be better, even though there is no evidence to support it.
- 'oilies' who worship gas guzzlers (manufacturers, oil companies, and 'sheeple' who blindly follow them) who are desperate to find reasons that EVs cannot be equivalent to ICE. Remember that GM fought Tesla in the J-1772 committee to limit the maximum J-1772 charging speed to 15 amps and, later the CCS committee to limit CCS to 50 KW, thus ensuring that an ICE was needed for long distance travel.
Its good to see some documented studies starting to appear. Before, only car companies could afford to abuse batteries to know the effects and those results were always hidden in proprietary internal reports.