How does Shakespeare present the attitudes of the young men in act 1, scene 1?

Shakespeare understood the importance of drawing in his audience from the first moments of the play, and we see that evidence in the beginning of Romeo and Juliet. The audience is presented with this group of young men who are boisterous and ready for a fight with pretty much anyone. They are hotheaded and full of themselves, prodding each other in the ongoing banter.
At the beginning of this scene, Gregory insults Sampson's ability to attract women, and Sampson replies, "’tis known I am a pretty piece of flesh." In these comments, we see that the young men aren't just full of anger but also sarcasm and sense of banter that fuels their rowdy scene.
We then see them pushing the boundaries as another group walks by, choosing to bite their thumbs at them as a mild source of insult. This engages the groups in a dispute, and a fight indeed breaks out.
Two characters emerge from this scene with character that will be important for the remainder of the play. Benvolio breaks up the fight, commenting, "You don’t know what you’re doing," and readers first see his sense of reason and rationality. On the other hand, Tybalt comments, "You’ve pulled out your sword to fight with these worthless servants? Turn around, Benvolio, and look at the man who’s going to kill you." Unlike Benvolio, Tybalt is seen to be insulting and antagonistic. This contrast is important for forthcoming conflict.

In this scene, Shakespeare presents the attitudes of the young men as being very macho and aggressive. This is shown through Sampson and Gregory, servants of the Capulet household, who are walking on the street and looking for some members of the Montague family to fight with.
In addition, through Sampson and Gregory, we learn more about their attitudes toward women. By talking about having sex with Montague women, especially virgins, the men are presented as being overtly sexual and keen to assert their masculinity through their sexual prowess.
With the arrival of Tybalt and Benvolio, Shakespeare reinforces the aggressive, pugnacious attitudes of the young men. Even though they are out in the street, they will not hold back their aggression. For them, the feud is about protecting the honor of their respective families, and this is a duty which they take very seriously.