Mr. Collins shows a strong degree of pride in many areas, particularly his belief that Elizabeth Bennet would accept his offer of marriage without question, and the fact that he does not believe that she is actually refusing him.
`"Really, Mr. Collins,'' cried Elizabeth with some warmth, ``you puzzle me exceedingly. If what I have hitherto said can appear to you in the form of encouragement, I know not how to express my refusal in such a way as may convince you of its being one.'' (Austen)
When Elizabeth is visiting Mr. Collins and his wife, Charlotte, and they get invited to dine as Rosings, Mr. Collins looks down on Elizabeth as if she is inferior and therefore will be embarrassed at the grand estate because she does not have fancy clothes to wear.
`"Do not make yourself uneasy, my dear cousin, about your apparel. Lady Catherine is far from requiring that elegance of dress in us, which becomes herself anddaughter. I would advise you merely to put on whatever of your clothes is superior to the rest, there is no occasion for any thing more. Lady Catherine will not think the worse of you for being simply dressed. She likes to have the distinction of rank preserved.'' (Austen)
The pompous Collins informs Elizabeth that Lady Catherine rather enjoys feeling superior to others, so Elizabeth can wear whatever she has, because Lady Catherine is so far above them that Elizabeth could not possibly have anything that might make her worthy of the great Lady's admiration anyway.
"Since Mr. Bennet has no sons, his 25-year-old nephew Mr. Collins is, to everyone's chagrin, the heir of his estate. He is also, in Lizzy's words, "a conceited, pompous, narrow-minded, silly man."
He has a way of insulting others from a sense of superiority, when he rather a buffoon who makes a fool of himself with his excessive slobbering all over Lady Catherine and he thinks that his actions are at the height of good behavior.