Is it Islamic for my parents to prevent me from marrying a Lebanese Shia man from a respectable and religious family just because of his nationality, despite our compatibility and my desire to make our existing relationship Halal?
Islam discourages racism and tribalism and encourages accepting any suitor who is mu'min and compatible. However people are complicated, especially when it comes to their expectations for their children's marriage and potential future descendants. I am sorry you have to go through that.