People growing up in the PRC have certainly benefitted from high levels of education, quality of life, and fairly wide global information access comparable to non-PRC Chinese environments like Hong Kong, Singapore, and Taiwan. So it’s perhaps unfair to be judged along class lines. But along with an inexperience with democratic representation, their cultural upbringing has also been less steeped in the traditional Chinese dimension (call it religious or superstitious as you prefer: celebration of religious festivals and holidays, ancestor worship, family over state as the elemental unit, even belief in “guanxi” and charity as a kind of karmic universal, etc.) that provides a considerable social lubricant in non-mainland Chinese cultures.
While this has begun to change in the past generation, it’s just another worldview difference that makes it hard to find common ground. Add that to the impact of nouveau-riche mainland tourists, and it’s easy to see how the different groups might find mutual trust and communication difficult, regardless of their historic suspicions. That makes me think it’s less arrogance, and more experience with misunderstandings that help perpetuate this distrust, and something that political agencies can easily amplify for their own purposes.
In my limited and distant view, I think it’s not just democracy that motivates the HK resistance, but also the potential erosion of traditional Chinese values that they see exhibited by the mainland.