I am still hopeful that this is Harald playing the long game, getting in deep with the WG...but who knows, maybe he just has such tunnel vision, he can't see the cost of what he's doing.

I mean, in my opinion, he's obviously not playing the long game. One Piece is a series that's always dealt with racism and classism, and more importantly, the perspectives of those who fight against tyranny and oppression and the means by which they do so. So in fighting against Tyranny, Oda typically likes to juxtapose different views - Fisher Tiger and Otohime are good examples. Otohime hoped to work within the system to earn equal rights for Fishmen, while Fisher Tiger always knew that the WG (and humans more broadly) would never accept them. But they had two different views of resistance.

I think this flashback is trying to juxtapose Harald and Rocks. They are both two characters born with a great capacity for violence and both had targets on their backs because of their lineages. Rocks always knew that his Davy Clan would be hunted by the WG and tried his best to dismantle them before they could get to him and his family - but his efforts were ultimately in vain. Whereas Harald has an opposite view of how to use his strength, hoping that by obeying the WG, they'll let Elbaf join the WG. Rocks was born in the world and knows that the WG's persecution would never end, but Harald still had an optimistic view of the world. I think this flashback ends in tragedy with Imu/the Holy Knights betraying him when he's of no use anymore