Why do online Chaoshan people disagree that their cultural language originated in southern Fujian?

Because part of ancient chaozhou people was moved from Fujian, and part of it was moved from Henan in the Central Plains to Chaozhou via Fujian, part of Chaozhou dialect has Minnan accent, and part of it is ancient Chinese brought from the Central Plains.

So Chaozhou dialect is different from Minnan dialect. Chaozhou dialect is a dialect formed by the combination of ancient Chinese and Minnan dialect, which retains many words of ancient Chinese. Therefore, the relationship between Chaozhou dialect and Minnan dialect is a cousin relationship, not a superior-subordinate relationship, nor a branch of Minnan dialect.

Three migrations

Central Plains immigrants entered Chaoshan three times from Fujian, namely Jin Dynasty, Sui and Tang Dynasties and the last years of Southern Song Dynasty. Because Fujian is vast and sparsely populated, many ancestors continued to move south to Chaoshan area. It can be said that every migration tide from the Central Plains will greatly increase the population of Chaoshan area.

It can be said that Chaoshan and Minnan are in the same cultural circle, and the degree of intimacy can be described by brotherhood, but there is not much difference between them, but they belong to two different provinces, Minnan belongs to Fujian, Chaoshan belongs to Guangdong, one is a brother and the other is a brother.