"Let us swallow them alive like Sheol, even whole, as those who go down to the pit"
There are two basic ethical principles for those who embrace wickedness and violence. Who benefits from the actions you do? Does your action harm others?
The way of the fool always violates one or both of these questions. Either the only one benefited by the action is oneself and/or others are or will be significantly damaged by the foolish action.
Solomon is screaming at us to notice the kinds of language and goals that the gang or thieves pursue. It is open foolishness masquerading as a focus of life.
This whole section deals with the lure of easy money and power through gangs, violence, and theft. Solomon is trying to get young men to turn away from the most destructive forms of foolishness: violence, gangs, and intimidation. This lure is so destructive and changes one's whole life so that there is no going back. These kinds of choices continually come up in life – choices to take the fool’s road through life or to take the harder, more disciplined, patient way called wisdom.
Yes, there are times when wisdom seems like the stupid choice, but selfishness and harm are always the wrong direction no matter the short-term payoff. Right now you might be facing this kind of choice – in business, in relationships, in government, in family. This is how the temptation comes. "If you just up your power and intimidation factor, you will win." "This is war and they need to lose big time so that you can win." "It is either them or you. Go for the win."
If your plan involves the destruction of others (with the exception of those who are immoral in their behavior and you are the approved instrument of justice), then it is the fool’s path. Don't go that way. Find a way for everybody to win. There is a way.