Main themes in this fanfiction could be numerous. Firstly, respect as the title implies. Harry respecting the goblins can be a starting point to explore the deep - seated prejudices in the wizarding world. It could also have a theme of social change, where Harry's respect for the goblins starts to shift the way wizards view them. Additionally, the theme of identity could be present. The goblins' identity within the wizarding world, how they are perceived and how they perceive themselves, could all be explored through Harry's newfound respect for them. This fanfiction might also touch on the theme of friendship, as Harry's respect could lead to a more amicable relationship between him and the goblins, breaking down the barriers that previously existed.
The themes could include respect, of course. Harry showing respect for the goblins might lead to a broader exploration of how different magical beings should respect each other's existence and rights. Also, there could be a theme of redemption, perhaps if the fanfiction involves Harry trying to make up for past wrongs that wizards have done to goblins. And cooperation might be another theme, as Harry could be working with the goblins towards a common goal.