"Which do you mean?" and turning round, he looked for a moment at Elizabeth, till catching her eye, he withdrew his own and coldly said, "She is tolerable; but not handsome enough to tempt me; and I am in no humour at present to give consequence to young ladies who are slighted by other men. You had better return to your partner and enjoy her smiles, for you are wasting your time with me." (Chapter 3)

I do not think your situation is comparable to Darcy's for two reasons. First, I do not see an indication that Darcy is a subdued personality as you suggest you were. IMO the evidence in Chapter 3 illustrates the contrary. He openly voiced his distain in a less than subtle manner so his opinions and judgments cannot be mistaken. He says Lizzy and other local ladies and the assembly itself are not good enough for him and he means it. Second, I think the people of Meryton were quite reasonable in expecting Darcy would be an agreeably mannered gentleman at their assembly. There is no indication Darcy was expected to act as agreeably as Bingley but that he fell below the lowest acceptable standard for being sociable and agreeable—he offends and hurts people. Darcy is a gentleman by birth but in this instance not so much by behavior—he skirts the line at the assembly IMO. His behavior is all the worse because he determined the people at the assembly did not deserve to be treated with attention or respect. He is actually being a terrible snob at the assembly and justifiably looses the good opinion the people of Meryton had bestowed upon him. ;D