Sir Walter bases peoples worth on their lineage, not their actions or character - he mocks Lord St Ives for his father being a poor curate like this somehow makes him less of a person. Titles aren't worth anything to him if they are earned. Which is funny because Baronet is a title that could be bought or "earned" (gifted for performing some duty for royalty), it is the lowest ranked title that can be inherited. For all his airs Sir Walter isn't even part of the nobility.