How does Hamlet judge those who have some “vicious mole” or defect, such as drunkenness? What does this reveal about his character?

Hamlet doesn't judge those with defects. In fact, this section describes how Hamlet understands it is an injustice for people to judge others based on their defects rather than their accomplishments. But he also knows that defects such as drunkeness harm a man/woman's reputation and good name. In this dialogue he warns those around him to safeguard their reputations because actions speak louder than words.

For the second part of your question, Hamlet doesn't approve of drinking (this goes with the answer above) and abhors the fact that King Claudius is a very heavy drinker. Hamlet feels that abolishing the festivity will set a better example for the rest of the court.